Steam reforming fuel processor, burner assembly, and methods of operating the same

ABSTRACT

Systems and methods for producing hydrogen gas with a fuel processing system that includes a hydrogen-producing region that produces hydrogen gas from a feed stream and a heating assembly that consumes a fuel stream to produce a heated exhaust stream for heating the hydrogen-producing region. In some embodiments, the heating assembly heats the hydrogen-producing region to at least a minimum hydrogen-producing temperature. In some embodiments, the rate at which an air stream is delivered to the heating assembly is controlled to selectively increase or decrease the temperature of the heated exhaust stream. In some embodiments, the feed stream and the fuel stream both contain a carbon-containing feedstock and at least 25 wt % water. In some embodiments, the feed and fuel streams have the same composition.

RELATED APPLICATIONS

This application is a divisional continuing application of, and claimspriority to, U.S. patent application Ser. No. 10/412,709, which wasfiled on Apr. 10, 2003 and which claims priority to U.S. ProvisionalPatent Application Ser. No. 60/372,748, which was filed on Apr. 14, 2002and is entitled “Steam Reforming Fuel Processor, Burner Assembly, andMethods of Operating the Same,” and to U.S. Provisional PatentApplication Ser. No. 60/392,397, which was filed on Jun. 27, 2002 and isentitled “Fuel Processing System with Diffusion Burner Assembly.” Thisapplication also claims priority to U.S. patent application Ser. No.12/044,799, which was filed on Mar. 7, 2008 and which is also adivisional continuing application of U.S. patent application Ser. No.10/412,709. The complete disclosures of the above-identifiedapplications are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure is directed generally to fuel processing and fuelcell systems, and more particularly, to burner assemblies for use insuch systems and to fuel processing and fuel cell systems containingthese burner assemblies.

BACKGROUND OF THE DISCLOSURE

Purified hydrogen is used in the manufacture of many products includingmetals, edible fats and oils, and semiconductors and microelectronics.Purified hydrogen is also an important fuel source for many energyconversion devices. For example, many fuel cells use purified hydrogenand an oxidant to produce an electrical potential. A series ofinterconnected fuel cells is referred to as a fuel cell stack, and thisstack may be referred to as a fuel cell system when combined withsources of oxidant and hydrogen gas. Various processes and devices maybe used to produce the hydrogen gas that is consumed by the fuel cells.

As used herein, a fuel processor is a device that produces hydrogen gasfrom a feed stream that includes one or more feedstocks. Examples offuel processors include steam and autothermal reformers, in which thefeed stream contains water and a carbon-containing feedstock, such as analcohol or a hydrocarbon, and partial oxidation and pyrolysis reactors,in which the feed stream is a carbon-containing feedstock. Fuelprocessors typically operate at elevated temperatures. Because thereforming and other fuel processing reactions are overall endothermic,the heat required to heat the fuel processors needs to be provided by aheating assembly, such as a burner, electrical heater or the like. Whenburners are used to heat the fuel processor, the burners typicallyutilize a combustible fuel stream, such as a combustible gas or acombustible liquid.

One such hydrogen-producing fuel processor is a steam reformer, in whichhydrogen gas is produced from a feed stream that includes acarbon-containing feedstock and water. Steam reforming is performed atelevated temperatures and pressures, and therefore steam reformerstypically include a heating assembly that provides heat for the steamreforming reaction, such as to maintain the reforming catalyst bed at aselected reforming temperature and to vaporize the feed stream. One typeof heating assembly is a burner, in which a combustible fuel stream iscombusted with air. Steam reformers conventionally utilize a feed streamthat is vaporized and reformed to produce a mixed gas stream containinghydrogen gas and other gases, and a fuel stream that has a differentcomposition that the feed stream and which is delivered to, and consumedby, the burner or other heating assembly to heat the steam reformer.

SUMMARY OF THE DISCLOSURE

The present disclosure is directed to a burner assembly, such as may beused in fuel processing and fuel cell systems, and to fuel processingand fuel cell systems containing burner assemblies according to thepresent disclosure. The burner assembly receives at least one fuelstream, mixes the stream with air and ignites the mixed stream toprovide heat for a fuel processor. In some embodiments, the burnerassembly is adapted to receive and vaporize a liquid combustible fuelstream, in other embodiments, the burner assembly is adapted to receivea gaseous combustible fuel stream, and in still other embodiments, theburner assembly is adapted to receive both liquid and gaseouscombustible fuel streams. In some embodiments, the burner assemblyreceives at least one combustible fuel stream that is produced by thefuel processing and/or fuel cell system with which the burner is used.In some embodiments, the burner assembly receives a fuel stream havingthe same composition as a stream that is delivered for non-combustionpurposes to another portion of the fuel processing and/or fuel cellsystem with which the burner assembly is used. In some embodiments, theburner assembly is adapted to receive and vaporize a fuel stream thatincludes the same carbon-containing feedstock and/or the same overallcomposition as the feed stream from which the steam reformer or otherfuel processor produces hydrogen gas. In some embodiments, the feedstream and the fuel stream have the same composition, and optionally areselectively delivered from the same supply. In some embodiments, theburner assembly is a diffusion burner assembly. In some embodiments, theburner assembly is an atomizing burner assembly. Methods for operating asteam reformer and burner assembly are also disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fuel processing system with a burnerassembly according to the present disclosure.

FIG. 2 is a schematic diagram of a fuel processing system with achemical carbon monoxide removal assembly according to the presentdisclosure.

FIG. 3 is a schematic diagram of a fuel cell system with a burnerassembly according to the present disclosure.

FIG. 4 is a schematic diagram of another fuel processor with a burnerassembly according to the present disclosure.

FIG. 5 is a schematic view of another burner assembly according to thepresent disclosure.

FIG. 6 is a schematic view of another burner assembly according to thepresent disclosure.

FIG. 7 is a schematic view of a fuel processor according to the presentdisclosure in which the hydrogen-producing region and the burnerassembly both receive the same liquid carbon-containing feedstock.

FIG. 8 is a schematic view showing a variation of the fuel processor ofFIG. 7, with a carbon-containing feedstock being delivered to thehydrogen-producing region and the burner assembly from the same supplystream.

FIG. 9 is a schematic view of a fuel processor according to the presentdisclosure in which the hydrogen-producing region and the burnerassembly both receive fuel, or feed, streams containing water and aliquid carbon-containing feedstock.

FIG. 10 is a schematic view showing a variation of the fuel processor ofFIG. 9, with the hydrogen-producing region and the burner assembly bothreceiving fuel, or feed, streams containing water and acarbon-containing feedstock from the same supply stream.

FIG. 11 is a schematic view showing another variation of the fuelprocessors of FIGS. 9 and 10.

FIG. 12 is a schematic view showing another burner assembly according tothe present disclosure.

FIG. 13 is a schematic view showing an ignition region of a burnerassembly that includes an atomization assembly that includes anatomizing orifice.

FIG. 14 is a schematic view of an ignition region of a burner assemblythat includes an atomization assembly that includes a nozzle with anatomizing orifice.

FIG. 15 is a schematic view of another ignition region of a burnerassembly that includes an atomization assembly that includes a nozzlewith an atomizing orifice.

FIG. 16 is a schematic view of an ignition region of a burner assemblythat includes an atomization assembly that includes an impingementmember that atomizes the feed stream.

FIG. 17 is a schematic view of another ignition region of a burnerassembly that includes an impingement member that atomizes the feedstream.

FIG. 18 is a schematic view of another ignition region of a burnerassembly according to the present disclosure that includes animpingement member that atomizes the feed stream.

FIG. 19 is a cross-sectional view of an ignition region of anotherburner assembly that includes an impingement member.

FIG. 20 is a cross-sectional view of the region of FIG. 19 taken alongthe line 20-20 in FIG. 19.

FIG. 21 is a cross-sectional view of another ignition region of a burnerassembly according to the present disclosure that also combusts abyproduct stream from the fuel processor.

FIG. 22 is a cross-sectional view of the region of FIG. 21, taken alongthe line 22-22 in FIG. 21.

FIG. 23 is a cross-sectional view of another ignition region of a burnerassembly according to the present disclosure.

FIG. 24 is a top plan view of the ignition region of FIG. 23 taken alongthe line 24-24 in FIG. 23.

FIG. 25 is a cross-sectional view of a portion of the distribution plateof the ignition region of FIG. 23 taken along the line 25-25 in FIG. 24.

FIG. 26 is a cross-sectional view of a variation of the ignition regionsof FIGS. 20 and 22 that includes an extension sleeve with a reduced-areaoutlet.

FIG. 27 is a top plan view of extension sleeve of the ignition region ofFIG. 26.

FIG. 28 is a cross-sectional view showing another variation of theignition regions of FIGS. 23 and 26.

FIG. 29 is an exploded cross-sectional view of the ignition region ofFIG. 28.

FIG. 30 is a cross-sectional view of a fuel processor that includes aburner assembly according to the present disclosure.

FIG. 31 is a cross-sectional view of another fuel processor thatincludes a burner assembly according to the present disclosure,

FIG. 32 is a cross-sectional view of the fuel processor of FIG. 31 takenalong the line 32-32 in FIG. 31.

FIG. 33 is an isometric view of another fuel processor with a burnerassembly according to the present disclosure.

FIG. 34 is an exploded isometric view of the fuel processor of FIG. 34.

FIG. 35 is a side elevation view of the fuel processor of FIGS. 33 and34 with the shroud, or cover assembly, removed.

FIG. 36 is bottom plan view of the fuel processor of FIG. 33.

FIG. 37 is a cross-sectional view of the fuel processor of FIG. 33 takenalong the line 37-37 in FIG. 36 and with the legs of the supportassembly removed.

FIG. 38 is a cross-sectional view of the fuel processor of FIG. 33 takenalong the line 38-38 in FIG. 36.

FIG. 39 is a cross-sectional view of the fuel processor of FIG. 33.

FIG. 40 is a schematic diagram of another burner assembly according tothe present disclosure.

FIG. 41 is a schematic diagram of another burner assembly according tothe present disclosure.

FIG. 42 is a schematic diagram of another burner assembly according tothe present disclosure.

FIG. 43 is a side cross-sectional view of another burner assemblyaccording to the present disclosure.

FIG. 44 is a fragmentary cross-sectional view showing variations of theburner assembly of FIG. 43.

FIG. 45 is a top plan view of another burner assembly according to thepresent disclosure.

FIG. 46 is a side cross-sectional view of the burner assembly of FIG.45, taken along the line 46-46 in FIG. 45.

FIG. 47 is an isometric view of a variant of the burner assembly of FIG.45.

FIG. 48 is an exploded isometric view of the burner assembly of FIG. 47.

FIG. 49 is an isometric view of a variation of the burner assembly ofFIGS. 45 and 47.

FIG. 50 is an isometric view of the burner assembly of FIG. 49 with aninstalled heating assembly.

FIG. 51 is an exploded isometric view of the burner assembly of FIG. 50.

FIG. 52 is an isometric view of another burner assembly according to thepresent disclosure.

FIG. 53 is a cross-sectional isometric view of the burner assembly ofFIG. 52.

FIG. 54 is a cross-sectional isometric view showing a variation of theburner assembly of FIG. 53.

FIG. 55 is a schematic diagram of a steam reformer with a burnerassembly according to the present disclosure.

FIG. 56 is a flowchart showing illustrative methods for using burnerassemblies according to the present disclosure.

DETAILED DESCRIPTION AND BEST MODE OF THE DISCLOSURE

A fuel processing system is shown in FIG. 1 and indicated generally at10. System 10 includes a fuel processor 12 that is adapted to produce aproduct hydrogen stream 14 containing hydrogen gas, and preferably atleast substantially pure hydrogen gas, from one or more feed streams 16.Fuel processor 12 is any suitable device, or combination of devices,that is adapted to produce hydrogen gas from feed stream(s) 16.Accordingly, processor 12 includes a hydrogen-producing region 19, inwhich a resultant stream 20 containing hydrogen gas is produced byutilizing any suitable hydrogen-producing mechanism(s). By this it ismeant that hydrogen gas is at least a primary constituent of stream 20.

Examples of suitable mechanisms for producing hydrogen gas from feedstream(s) 16 include steam reforming and autothermal reforming, in whichreforming catalysts are used to produce hydrogen gas from a feed streamcontaining a carbon-containing feedstock and water. Other suitablemechanisms for producing hydrogen gas include pyrolysis and catalyticpartial oxidation of a carbon-containing feedstock, in which case thefeed stream does not contain water. Still another suitable mechanism forproducing hydrogen gas is electrolysis, in which case the feedstock iswater. Examples of suitable carbon-containing feedstocks include atleast one hydrocarbon or alcohol. Examples of suitable hydrocarbonsinclude methane, propane, natural gas, diesel, kerosene, gasoline andthe like. Examples of suitable alcohols include methanol, ethanol, andpolyols, such as ethylene glycol and propylene glycol.

Feed stream(s) 16 may be delivered to fuel processor 12 via any suitablemechanism. While a single feed stream 16 is shown in FIG. 1, it iswithin the scope of the disclosure that more than one stream 16 may beused and that these streams may contain the same or differentfeedstocks. This is schematically illustrated by the inclusion of asecond feed stream 16 in dashed lines in FIG. 1. When feed stream 16contains two or more components, such as a carbon-containing feedstockand water, the components may be delivered in the same or different feedstreams. For example, when the fuel processor is adapted to producehydrogen gas from a carbon-containing feedstock and water, thesecomponents are typically delivered in separate streams when they are notmiscible with each other. This is schematically illustrated in dashedlines in FIG. 1, in which reference numeral 17 represents water andreference numeral 18 represents a carbon-containing feedstock, such asmany hydrocarbons, that is not miscible with water. When thecarbon-containing feedstock is miscible with water, the feedstock istypically, but not required to be, delivered with the water component offeed stream 16, such as shown in the subsequently described FIG. 2. Forexample, when the fuel processor receives a feed stream containing waterand a water-soluble alcohol, such as methanol, these components may bepremixed and delivered as a single stream.

In FIG. 1, feed stream 16 is shown being delivered to fuel processor 12by a feedstock delivery system 22, which schematically represents anysuitable mechanism, device or combination thereof for selectivelydelivering the feed stream to the fuel processor. For example, thedelivery system may include one or more pumps that deliver thecomponents of stream 16 from one or more supplies. Additionally, oralternatively, system 22 may include a valve assembly adapted toregulate the flow of the components from a pressurized supply. Thesupplies may be located external of the fuel processing system, or maybe contained within or adjacent the system. When feed stream 16 isdelivered to the fuel processor in more than one stream, the streams maybe delivered by the same or separate feed stream delivery systems.

An example of a hydrogen-producing mechanism in which feed stream 16comprises water and a carbon-containing feedstock is steam reforming. Ina steam reforming process, hydrogen-producing region 19 contains areforming catalyst 23, as indicated in dashed lines in FIGS. 1 and 2. Insuch an embodiment, the fuel processor may be referred to as a steamreformer, hydrogen-producing region 19 may be referred to as a reformingregion, and resultant, or mixed gas, stream 20 may be referred to as areformate stream. Examples of suitable steam reforming catalysts includecopper-zinc formulations of low temperature shift catalysts and achromium formulation sold under the trade name KMA by Süd-Chemie,although others may be used. The other gases that are typically presentin the reformate stream include carbon monoxide, carbon dioxide,methane, steam and/or unreacted carbon-containing feedstock.

Steam reformers typically operate at temperatures in the range of 200°C. and 700° C., and at pressures in the range of 50 psi and 300 psi,although temperatures and pressures outside of this range are within thescope of the invention. When the carbon-containing feedstock is analcohol, the steam reforming reaction will typically operate in atemperature range of approximately 200-500° C., and when thecarbon-containing feedstock is a hydrocarbon, a temperature range ofapproximately 400-800° C. will be used for the steam reforming reaction.As such, feed stream 16 is typically delivered to the fuel processor ata selected pressure, such as a pressure within the illustrative rangepresented above.

In many applications, it is desirable for the fuel processor to produceat least substantially pure hydrogen gas. Accordingly, the fuelprocessor may utilize a process that inherently produces sufficientlypure hydrogen gas. When the resultant stream contains sufficiently purehydrogen gas and/or sufficiently low concentrations of one or morenon-hydrogen components for a particular application, product hydrogenstream 14 may be formed directly from resultant stream 20. However, inmany hydrogen-producing processes, resultant stream 20 will be a mixedgas stream that contains hydrogen gas and other gases. Similarly, inmany applications, the product hydrogen stream may be substantially purebut still contain concentrations of one or more non-hydrogen componentsthat are harmful or otherwise undesired for the application for whichthe product hydrogen stream is intended to be used.

Accordingly, fuel processing system 10 may (but is not required to)further include a separation region 24, in which the resultant, or mixedgas, stream is separated into a hydrogen-rich stream 26 and at least onebyproduct stream 28. Hydrogen-rich stream 26 contains at least one of agreater hydrogen purity than the resultant stream and a reducedconcentration of one or more of the other gases or impurities that werepresent in the resultant stream. Separation region 24 is schematicallyillustrated in FIG. 1, where resultant stream 20 is shown beingdelivered to an optional separation region 24. As shown in FIG. 1,product hydrogen stream 14 is formed from hydrogen-rich stream 26.Byproduct stream 28 may be exhausted, sent to a burner assembly or othercombustion source, used as a heated fluid stream, stored for later use,or otherwise utilized, stored or disposed of. It is within the scope ofthe disclosure that byproduct stream 28 may be emitted from theseparation region as a continuous stream responsive to the delivery ofresultant stream 20 to the separation region, or intermittently, such asin a batch process or when the removed portion of the resultant streamis retained at least temporarily in the separation region.

Separation region 24 includes any suitable device, or combination ofdevices, that are adapted to reduce the concentration of at least onecomponent of resultant stream 20. In most applications, hydrogen-richstream 26 will have a greater hydrogen purity than resultant stream 20.However, it is also within the scope of the disclosure that thehydrogen-rich stream will have a reduced concentration of one or morenon-hydrogen components that were present in resultant stream 20, yethave the same, or even a reduced overall hydrogen purity as theresultant stream. For example, in some applications where producthydrogen stream 14 may be used, certain impurities, or non-hydrogencomponents, are more harmful than others. As a specific example, inconventional fuel cell systems, carbon monoxide may damage a fuel cellstack if it is present in even a few parts per million, while otherpossible non-hydrogen components, such as water, will not damage thestack even if present in much greater concentrations. Therefore, in suchan application, a suitable separation region may not increase theoverall hydrogen purity, but it will reduce the concentration of anon-hydrogen component that is harmful, or potentially harmful, to thedesired application for the product hydrogen stream.

Illustrative examples of suitable devices for separation region 24include one or more hydrogen-selective membranes 30, chemical carbonmonoxide removal assemblies 32, and pressure swing adsorption systems38. It is within the scope of the disclosure that separation region 24may include more than one type of separation device, and that thesedevices may have the same or different structures and/or operate by thesame or different mechanisms.

Hydrogen-selective membranes 30 are permeable to hydrogen gas, but arelargely impermeable to other components of resultant stream 20.Membranes 30 may be formed of any hydrogen-permeable material suitablefor use in the operating environment and parameters in which separationregion 24 is operated. Examples of suitable materials for membranes 30include palladium and palladium alloys, and especially thin films ofsuch metals and metal alloys. Palladium alloys have proven particularlyeffective, especially palladium with 35 wt % to 45 wt % copper. Apalladium-copper alloy that contains approximately 40 wt % copper hasproven particularly effective, although other relative concentrationsand components may be used within the scope of the invention.

Hydrogen-selective membranes are typically formed from a thin foil thatis approximately 0.001 inches thick. It is within the scope of thepresent invention, however, that the membranes may be formed from otherhydrogen-permeable and/or hydrogen-selective materials, including metalsand metal alloys other than those discussed above as well asnon-metallic materials and compositions, and that the membranes may havethicknesses that are greater or less than discussed above. For example,the membrane may be made thinner, with commensurate increase in hydrogenflux. Examples of suitable mechanisms for reducing the thickness of themembranes include rolling, sputtering and etching. A suitable etchingprocess is disclosed in U.S. Pat. No. 6,152,995, the complete disclosureof which is hereby incorporated by reference for all purposes. Examplesof various membranes, membrane configurations, and methods for preparingthe same are disclosed in U.S. Pat. Nos. 6,221,117, 6,319,306, and6,537,352, the complete disclosures of which are hereby incorporated byreference for all purposes.

Chemical carbon monoxide removal assemblies 32 are devices thatchemically react carbon monoxide, if present in resultant stream 20, toform other compositions that are not as potentially harmful as carbonmonoxide. Examples of chemical carbon monoxide removal assembliesinclude water-gas shift reactors and other devices that convert carbonmonoxide to carbon dioxide, and methanation catalyst beds that convertcarbon monoxide and hydrogen to methane and water. It is within thescope of the disclosure that fuel processing system 10 may include morethan one type and/or number of chemical removal assemblies 32. FIG. 2provides a graphical depiction of a fuel processing system that includesa separation region 24 with a chemical removal assembly 32. In theillustrated example, assembly 32 includes a methanation region 34 thatincludes a methanation catalyst 35. Methanation catalyst 35 convertscarbon monoxide and carbon dioxide into methane and water, both of whichwill not damage a PEM fuel cell stack. Accordingly, region 34 may bereferred to as including at least one methanation catalyst bed.Separation region 32 may also include a reforming region 36 thatcontains reforming catalyst 23 to convert any unreacted feedstock intohydrogen gas. In such an embodiment, it is preferable that the reformingcatalyst is upstream from the methanation catalyst so as not toreintroduce carbon dioxide or carbon monoxide downstream of themethanation catalyst. When used to treat the hydrogen-rich stream fromone or more hydrogen-selective membranes, reforming region 36 may bedescribed as being a secondary, or polishing, reforming region, and itmay also be described as being downstream from the primary reformingregion and/or the hydrogen selective membrane(s).

Pressure swing adsorption (PSA) is a chemical process in which gaseousimpurities are removed from resultant stream 20 based on the principlethat certain gases, under the proper conditions of temperature andpressure, will be adsorbed onto an adsorbent material more strongly thanother gases. Typically, it is the impurities that are adsorbed and thusremoved from resultant stream 20. The success of using PSA for hydrogenpurification is due to the relatively strong adsorption of commonimpurity gases (such as CO, CO₂, hydrocarbons including CH₄, and N₂) onthe adsorbent material. Hydrogen adsorbs only very weakly and sohydrogen passes through the adsorbent bed while the impurities areretained on the adsorbent material. Impurity gases such as NH₃, H₂S, andH₂O adsorb very strongly on the adsorbent material and are thereforeremoved from stream 20 along with other impurities. Impurity gases suchas NH₃, H₂S, and H₂O adsorb very strongly on the adsorbent material andare therefore removed from stream 20 along with other impurities. If theadsorbent material is going to be regenerated and these impurities arepresent in stream 20, separation region 24 preferably includes asuitable device that is adapted to remove these impurities prior todelivery of stream 20 to the adsorbent material because it is moredifficult to desorb these impurities.

Adsorption of impurity gases occurs at elevated pressure. When thepressure is reduced, the impurities are desorbed from the adsorbentmaterial, thus regenerating the adsorbent material. Typically, PSA is acyclic process and requires at least two beds for continuous (as opposedto batch) operation. Examples of suitable adsorbent materials that maybe used in adsorbent beds are activated carbon and zeolites, especially5 Å (5 angstrom) zeolites. The adsorbent material is commonly in theform of pellets and it is placed in a cylindrical pressure vesselutilizing a conventional packed-bed configuration. It should beunderstood, however, that other suitable adsorbent materialcompositions, forms and configurations may be used.

PSA system 38 also provides an example of a device for use in separationregion 24 in which the byproducts, or removed components, are notdirectly exhausted from the region as a gas stream concurrently with theseparation of the resultant stream. Instead, these components areremoved when the adsorbent material is regenerated or otherwise removedfrom the separation region.

In FIG. 1, separation region 24 is shown within fuel processor 12. It iswithin the scope of the disclosure that region 24, when present, mayalternatively be separately located downstream from the fuel processor,as is schematically illustrated in dash-dot lines in FIG. 1. It is alsowithin the scope of the disclosure that separation region 24 may includeportions within and external fuel processor 12.

In the context of a fuel processor that is adapted to produce a producthydrogen stream that will be used as a feed, or fuel, stream for a fuelcell stack, the fuel processor preferably is adapted to producesubstantially pure hydrogen gas, and even more preferably, the fuelprocessor is adapted to produce pure hydrogen gas. For the purposes ofthe present disclosure, substantially pure hydrogen gas is greater than90% pure, preferably greater than 95% pure, more preferably greater than99% pure, and even more preferably greater than 99.5% pure. Suitablefuel processors for producing streams of at least substantially purehydrogen gas are disclosed in U.S. Pat. Nos. 6,319,306, 6,221,117,5,997,594, 5,861,137, pending U.S. patent application Ser. No.09/802,361, which was filed on Mar. 8, 2001 and is entitled “FuelProcessor and Systems and Devices Containing the Same,” and U.S. patentapplication Ser. No. 10/407,500, which was filed on Apr. 4, 2003, isentitled “Steam Reforming Fuel Processor,” and which claims priority toU.S. Provisional Patent Application Ser. No. 60/372,258. The completedisclosures of the above-identified patents and patent applications arehereby incorporated by reference for all purposes.

Product hydrogen stream 14 may be used in a variety of applications,including applications where high purity hydrogen gas is utilized. Anexample of such an application is as a fuel, or feed, stream for a fuelcell stack. A fuel cell stack is a device that produces an electricalpotential from a source of protons, such as hydrogen gas, and anoxidant, such as oxygen gas. Accordingly, a fuel cell stack may beadapted to receive at least a portion of product hydrogen stream 14 anda stream of oxygen (which is typically delivered as an air stream), andto produce an electric current therefrom. This is schematicallyillustrated in FIG. 3, in which a fuel cell stack is indicated at 40 andproduces an electric current, which is schematically illustrated at 41.In such a configuration, in which the fuel processor or fuel processingsystem is coupled to a fuel cell stack, the resulting system may bereferred to as a fuel cell system 42 because it includes a fuel cellstack and a source of fuel for the fuel cell stack. It is within thescope of the present disclosure that fuel processors and burnerassemblies according to the present disclosure may be used inapplications that do not include a fuel cell stack.

When stream 14 is intended for use in a fuel cell stack, compositionsthat may damage the fuel cell stack, such as carbon monoxide and carbondioxide, may be removed from the hydrogen-rich stream, if necessary,such as by separation region 24. For fuel cell stacks, such as protonexchange membrane (PEM) and alkaline fuel cell stacks, the concentrationof carbon monoxide is preferably less than 10 ppm (parts per million).Preferably, the concentration of carbon monoxide is less than 5 ppm, andeven more preferably, less than 1 ppm. The concentration of carbondioxide may be greater than that of carbon monoxide. For example,concentrations of less than 25% carbon dioxide may be acceptable.Preferably, the concentration is less than 10%, and even morepreferably, less than 1%. Especially preferred concentrations are lessthan 50 ppm. It should be understood that the acceptable minimumconcentrations presented herein are illustrative examples, and thatconcentrations other than those presented herein may be used and arewithin the scope of the present invention. For example, particular usersor manufacturers may require minimum or maximum concentration levels orranges that are different than those identified herein.

Fuel cell stack 40 contains at least one, and typically multiple, fuelcells 44 that are adapted to produce an electric current from theportion of the product hydrogen stream 14 delivered thereto. A fuel cellstack typically includes multiple fuel cells joined together betweencommon end plates 48, which contain fluid delivery/removal conduits.Examples of suitable fuel cells include proton exchange membrane (PEM)fuel cells and alkaline fuel cells. Others include solid oxide fuelcells, phosphoric acid fuel cells, and molten carbonate fuel cells.

The electric current produced by stack 40 may be used to satisfy theenergy demands, or applied load, of at least one associatedenergy-consuming device 46. Illustrative examples of devices 46 include,but should not be limited to motor vehicles, recreational vehicles,construction or industrial vehicles, boats or other seacraft, tools,lights or lighting assemblies, appliances (such as household or otherappliances), households or other dwellings, offices or other commercialestablishments, computers, signaling or communication equipment, etc.Similarly, stack 40 may be used to satisfy the power requirements offuel cell system 42. It should be understood that device 46 isschematically illustrated in FIG. 3 and is meant to represent one ormore devices, or collection of devices, that are adapted to drawelectric current from the fuel cell system.

Fuel cell stack 40 may receive all of product hydrogen stream 14. Someor all of stream 14 may additionally, or alternatively, be delivered,via a suitable conduit, for use in another hydrogen-consuming process,burned for fuel or heat, or stored for later use. As an illustrativeexample, a hydrogen storage device 50 is shown in dashed lines in FIG.3. Device 50 is adapted to store at least a portion of product hydrogenstream 14. For example, when the demand for hydrogen gas by stack 40 isless than the hydrogen output of fuel processor 12, the excess hydrogengas may be stored in device 50. Illustrative examples of suitablehydrogen storage devices include hydride beds and pressurized tanks.Although not required, a benefit of system 10 or 42 including a supplyof stored hydrogen is that this supply may be used to satisfy thehydrogen requirements of stack 40, or the other application for whichstream 14 is used, in situations when processor 12 is not able to meetthese hydrogen demands. Examples of these situations include when thefuel processor is starting up from a cold, or inactive state, ramping upfrom an idle state, offline for maintenance or repair, and when thestack or application is demanding a greater flow rate of hydrogen gasthan the maximum available production from the fuel processor.Additionally or alternatively, the stored hydrogen may also be used as acombustible fuel stream to heat the fuel processing or fuel cell system.Fuel processing systems that are not directly associated with a fuelcell stack may still include at least one hydrogen-storage device,thereby enabling the product hydrogen streams from these fuel processingsystems to also be stored for later use.

Fuel cell system 42 may also include a battery 52 or other suitableelectricity-storing device that is adapted to store electricity producedby stack 40. Similar to the above discussion regarding excess hydrogen,stack 40 may produce electricity in excess of that necessary to satisfythe load exerted, or applied, by device 46, including the load requiredto power system 42. In further similarity to the above discussion ofexcess hydrogen gas, this excess supply may be transported from thesystem for use in other applications and/or stored for later use by thesystem. For example, the battery or other storage device may providepower for use by system 42 during startup or other applications in whichthe system is not producing electricity and/or hydrogen gas. In FIG. 3,flow-regulating structures are generally indicated at 54 andschematically represent any suitable manifold, valves, controllers andthe like for selectively delivering hydrogen and electricity to device50 and battery 52, respectively, and to draw the stored hydrogen andelectricity therefrom.

In FIG. 1, fuel processor 10 is shown including a shell 68 in which atleast the hydrogen-producing region, and optionally the separationregion, is contained. Shell 68, which also may be referred to as ahousing, enables the components of the steam reformer or other fuelprocessor to be moved as a unit. It also protects the components of thefuel processor from damage by providing a protective enclosure andreduces the heating demand of the fuel processor because the componentsof the fuel processor may be heated as a unit. Shell 68 may, but doesnot necessarily, include insulating material 70, such as a solidinsulating material, blanket insulating material, and/or an air-filledcavity. It is within the scope of the invention, however, that the fuelprocessor may be formed without a housing or shell. When fuel processor10 includes insulating material 70, the insulating material may beinternal the shell, external the shell, or both. When the insulatingmaterial is external a shell containing the above-described reforming,separation and/or polishing regions, the steam reformer may furtherinclude an outer cover or jacket 72 external the insulation, asschematically illustrated in FIG. 1.

It is further within the scope of the invention that one or more of thecomponents of fuel processor 10 may either extend beyond the shell or belocated external at least shell 68. For example, and as discussed,separation region 24 may be located external shell 68, such as with theseparation being coupled directly to the shell (as schematicallyillustrated in FIG. 4) or being spaced-away from the shell but in fluidcommunication therewith by suitable fluid-transfer conduits (asindicated in dash-dot lines in FIG. 1). As another example, a portion ofhydrogen-producing region 19 (such as portions of one or more reformingcatalyst beds) may extend beyond the shell, such as indicatedschematically with a dashed line in FIG. 1.

Fuel cell and fuel processing systems have been very schematicallyillustrated in FIGS. 1-4, and it should be understood that these systemsoften include additional components, such as air/oxidant supplies anddelivery systems, heat exchange assemblies and/or sources, controllers,sensors, valves and other flow controllers, power management modules,etc. Similarly, although a single fuel processor 12 and/or a single fuelcell stack 40 are shown in various ones of FIGS. 1-4, it is within thescope of the disclosure that more than one of either or both of thesecomponents may be used.

As also shown in various ones of FIGS. 1-4, fuel processing (and fuelcell) systems according to the present disclosure include a heatingassembly 60 that is adapted to heat at least the hydrogen-producingregion 19 of the fuel processor. In systems according to the presentdisclosure, heating assembly 60 includes a burner assembly 62. Burnerassembly 62 is adapted to receive at least one fuel stream 64 and tocombust the fuel stream in the presence of air to provide a hotcombustion stream 66 that may be used to heat at least thehydrogen-producing region 19 of the fuel processor. As discussed in moredetail herein, air may be delivered to the burner assembly via a varietyof mechanisms. In FIG. 4, an air stream 74 is shown in solid lines, witha dashed line being used to graphically indicate that it is within thescope of the disclosure for the air stream to additionally oralternatively be delivered to the burner assembly with at least one ofthe fuel streams 64 for the burner assembly. It is within the scope ofthe disclosure that combustion stream 66 may additionally oralternatively be used to heat other portions of the fuel processingand/or fuel cell systems with which burner assembly 62 is used. In FIGS.1-4, burner assembly 62 is shown in an overlapping relationship withfuel processor 12 to graphically represent that it is within the scopeof the disclosure that the burner assembly may be located partially orcompletely within the fuel processor, such as being at least partiallywithin shell 68, and/or that at least a portion, or all, of the burnerassembly may be located external the fuel processor. In this latterembodiment, the hot combustion gases from the burner assembly will bedelivered via suitable heat transfer conduits to the fuel processor orother portion of the systems to be heated.

As indicated in FIG. 4 in dashed lines, fuel processors 12 according tothe present disclosure may include a vaporization region 69 that isadapted to receive a liquid feed stream 16 (or a liquid component offeed stream 16, such as a stream of water 17 or a stream of a liquidcarbon-containing feedstock 76) and to vaporize the feed stream (orportion thereof) prior to delivery to the hydrogen-producing region ofthe fuel processor. As indicated schematically in FIG. 4, heated exhauststream 66 from the heating assembly may be used to vaporize the feedstream in vaporization region 69 and/or otherwise heat the feed stream.It is within the scope of the disclosure that fuel processor 12 may beconstructed without a vaporization region and/or that the fuel processoris adapted to receive a feed stream that is gaseous or that has alreadybeen vaporized.

In FIG. 5, another illustrative heating assembly 60 with a burnerassembly 62 is schematically illustrated. As shown, burner assembly 62includes an ignition region 86 in which the fuel and air streams (64 and74) are ignited to initiate the combustion thereof. Region 86 includesan ignition source 88, which is any suitable structure or device forigniting the fuel and air streams. Examples of suitable ignition sources88 include at least one of a spark plug, a glow plug, a pilot light, acombustion catalyst, glow plugs in combination with combustioncatalysts, electrically heated ceramic igniters, and the like. Thestreams are ignited and the combustion thereof produces a heated exhauststream 66, which typically is exhausted from the ignition region to acombustion chamber 92 or other heat transfer region of the steamreformer or fuel processing system. It is within the scope of thedisclosure that the combustion initiated in ignition region 86 may becompleted in a variety of locations within the burner assembly and/orfuel processor being heated by the burner assembly. For example, thecombustion may be fully completed in the ignition region, partiallycompleted in the ignition region and partially completed in thecombustion region, partially completed in the ignition region, thecombustion region and a portion of the fuel processor external thecombustion region, etc.

When fuel stream 64 is a gaseous stream, it can be mixed and ignitedwith air stream 74 to produce exhaust stream 66. However, some fuelstreams 64 are liquid-phase fuel streams at the operating parameters atwhich the fuel stream is delivered to burner assembly 62, namely atemperature in the range of ambient (approximately 25° C.) toapproximately 100° C. and a pressure in the range of 50-200 psi, andmore typically 100-150 psi. It should be understood that the operatingparameters discussed above are not intended to be exclusive examples.Instead, they are meant to illustrate typical parameters, withparameters outside of these ranges still being within the scope of theinvention. For example, the fuel stream may be heated, through heatexchange or otherwise, before being delivered to the burner assembly,but this heating is not required, nor necessarily useful in manyembodiments.

In the context of liquid-phase, or liquid, fuel streams, such as analcohol like methanol or ethanol or a hydrocarbon like methane, ethane,gasoline, kerosene, diesel, etc., the burner assembly preferablyincludes an atomization assembly 94. This is illustrated graphically inFIG. 6, in which the liquid fuel stream is indicated at 82 and containsa liquid carbon-containing feedstock 76, and in which the burnerassembly that is adapted to receive and atomize the liquid fuel streamis indicated at 80 and may be referred to as an atomizing burnerassembly. As used herein, “liquid” is meant to refer to fuel streamsthat are at least 95% liquid-phase at the operating parameters at whichthe fuel stream is delivered to the burner assembly, and preferably atleast approximately 99% liquid. It should be understood that even a“completely” liquid-phase stream may include a small (typically lessthan 1%) gas phase, such as produced by off gassing as the stream isheated. Atomization assembly 94 includes any suitable device orcombination of devices that are adapted to convert liquid fuel stream 82into an aerosol fuel stream 82′ that can be mixed with air stream 74 andcombusted, or ignited, to produce heated exhaust stream 66. This iscontrasted with vaporizing burner assemblies that heat a liquid fuelstream until the fuel stream changes phases to a vapor phase.Illustrative examples of suitable atomization assemblies are discussedin more detail herein.

As discussed, many conventional fuel processors, such as steam andautothermal reformers and pyrolysis and partial oxidation reactors,require a carbon-containing feedstock that is used in thehydrogen-producing reaction, and then a separate fuel stream that isused as a fuel source for the burner assembly. As such, these fuelprocessors require a separate source, pump or other delivery assembly,transport conduits and flow-regulating devices, etc. According to anaspect of the present disclosure, a liquid-phase carbon-containingfeedstock 76 is used for both the carbon-containing feedstock portion offeed stream 16 and fuel stream 82 for burner assembly 80, such asschematically illustrated in FIG. 7. As shown, liquid carbon-containingfeedstock 76 is delivered to both burner assembly 80 andhydrogen-producing region 19. FIG. 7 has been shown in fragmentary viewbecause fuel processor 12 may have a wide variety of configurations,such as configurations that do not include a separation region, thatutilize more than one type or number of separation mechanism, etc. It isintended that the fragmentary fuel processor shown in FIG. 7 (andsubsequent Figures) schematically represents any of theseconfigurations, as well as any of the steam reformers and other fuelprocessors described, illustrated and/or incorporated herein.

FIG. 8 is similar to FIG. 7, except that the liquid carbon-containingfeedstock 76 is delivered as a single stream to valve assembly 96, inwhich the carbon-containing feedstock is selectively delivered to atleast one of the burner assembly and the hydrogen-producing region.Valve assembly 96 may include any suitable structure for selectivelydividing the stream of carbon-containing feedstock between the burnerassembly and the hydrogen-producing region. The range of possibleconfigurations includes the burner assembly receiving all of thecarbon-containing feedstock, the hydrogen-producing region receiving allof the carbon-containing feedstock, or both the burner assembly and thehydrogen-producing region receiving carbon-containing feedstock. Asdiscussed herein, the distribution of the carbon-containing feedstockdepends at least in part upon the particular carbon-containing feedstockbeing used, whether byproduct stream 28 is also used as a fuel forburner assembly 80 and the particular mode of operation of the fuelprocessor, such as an idle mode, a startup mode, or a hydrogen-producingmode.

The distribution of feedstock 76 between the hydrogen-producing regionand the burner assembly may be manually controlled. However, in manyembodiments, it may be desirable for the distribution to be at leastpartially automated, such as by system 10 including a controller 98 thatselectively regulates the delivery of feedstock 76 between thehydrogen-producing region and the burner assembly. An example of asuitable controller for a steam reforming fuel processor is disclosed inU.S. Pat. No. 6,383,670, the complete disclosure of which is herebyincorporated by reference.

Further reduction in the supplies, delivery systems, flow regulators,delivery conduits and the like may be achieved according to anotheraspect of the present disclosure by feed stream 16 and fuel stream 82both containing the same liquid carbon-containing feedstock 76 and water17, with the water forming at least approximately 25% of the stream andthe carbon-containing feedstock preferably being miscible in water. Thisis schematically illustrated in FIGS. 9 and 10, in which this compositestream is indicated at 78. Streams 16 and 82 may have nearly, orcompletely, identical compositions, and may be entirely formed fromstream 78. It is within the scope of the disclosure, however, that atleast one of streams 16 and 82 may have at least one additionalcomponent or additional amount of water or carbon-containing feedstockadded thereto prior to consumption of the stream by the burner assemblyor hydrogen-producing region. As discussed previously, in the context ofa steam reformer or other fuel processor that produces hydrogen gas fromwater and a carbon-containing feedstock, feed stream 16 is at leastsubstantially, and typically essentially entirely, comprised of amixture of water and a liquid-phase carbon-containing feedstock 76 thatis preferably water-soluble. As such, a single stream containing water17 and carbon-containing feedstock 76 can be consumed as both thehydrogen-producing feed stream 16, as well as the burner fuel stream 82.

Similar to the previously discussed alternatives of FIGS. 7 and 8 (whereonly the carbon-containing feedstock component of feed stream 16 wasdelivered to burner assembly 80), feed stream 78 may be selectivelydelivered to burner assembly 80 and hydrogen-producing region 19 inseparate streams from the same or a different source. Alternatively, andas schematically illustrated in FIG. 10, a single feed stream 78 may bedelivered to the fuel processor, and more specifically to a valveassembly 96, where the stream is selectively divided between the burnerassembly and the hydrogen-producing region. A controller 98, which maybe a computerized or other electronic controller or preprogrammedcontroller, is also shown in dashed lines in FIG. 10. Controller 98 maybe located internal or external fuel processor 12, and/or may includeboth internal and external components.

The relative amounts of water 17 and liquid carbon-containing feedstock76 in streams 16 and 78 may vary, and in part will depend upon theparticular carbon-containing feedstock being used. The relativeconcentrations of these components may be expressed in terms of a ratioof water to carbon. When feedstock 76 is methanol, a 1:1 ratio hasproven effective. When feedstock 76 is ethanol, a ratio of 2-3:1 hasproven effective. When feedstock 76 is a hydrocarbon, a ratio ofapproximately 3:1 is typically used. However, the illustrative ratiosdescribed above are not meant to be exclusive ratios within the scope ofthe invention.

In FIG. 11, a variation of the configuration of FIG. 10 is shown toillustrate that it is within the scope of the invention that the valveassembly may be located either internal or external fuel processor 10.FIG. 11 also illustrates that when the fuel processor includes or isotherwise associated with a separation region 24 that produces a gaseousbyproduct stream 28, the gaseous byproduct stream 28 may be delivered tothe burner assembly to be used as a gaseous fuel for the burnerassembly. This gaseous fuel may supplement the liquid fuel discussedabove (such as carbon-containing feedstock 76 or feed stream 16), or mayitself contain sufficient heating value for certain steam reformers orother fuel processors and/or certain operating configurations of thefuel processors.

As discussed above, in the context of burner assemblies 80 according tothe present disclosure, the carbon-containing feedstock consumed in boththe hydrogen-producing region and the burner assembly is a liquid at theoperating parameters at which it is delivered to the burner assembly. Asalso discussed, burner assembly 80 includes an atomization assembly 94that is adapted to atomize the liquid fuel stream (82) to produce agaseous, or aerosol, stream (82′) that is ignited in ignition region 86with air stream 74. When the liquid fuel steam has the same compositionas the feed stream for a steam reformer or other fuel processor thatproduces hydrogen gas from water and a carbon-containing feedstock, theliquid fuel stream therefore contains a substantial water component(typically at least 25%), the stream is a liquid stream, and atomizationassembly 94 produces an aerosol, or gaseous, stream 78′ therefrom, asschematically illustrated in FIG. 12. For the purpose of brevity, thefollowing discussion of atomization assembly 94 will discuss a fuelstream in the form of a liquid stream 78 of water 17 andcarbon-containing feedstock 76, with stream 78 having the samecomposition as the feed stream 16 for a steam reformer or other fuelprocessor that is adapted to produce from water and a carbon-containingfeedstock a resultant stream 20 in which hydrogen gas is a primarycomponent. However, it is within the scope of the present disclosurethat the burner assemblies 80 and/or atomization assemblies 94illustrated and/or described herein may also be used with a liquidcarbon-containing feedstock without water, such as when the feedstock isa hydrocarbon that is not miscible in water. Similarly, and as discussedpreviously, it is also within the scope of the disclosure that stream 78may be used to form the feed/fuel streams for both the fuel processorand the burner assembly, but at least one of these streams may have atleast one additional component or additional amount of water orcarbon-containing feedstock added thereto.

An illustrative example of a suitable structure for atomization assembly94 is shown in FIG. 12 and includes an orifice 100 to which feed stream78 is delivered under pressure, such as at a pressure in the range of50-200 psi, and more typically approximately 100-150 psi. Orifice 100 issized to reduce the liquid feed stream into an aerosol, or gaseous,stream 78′ having sufficiently small droplets that the stream will tendto mix and disperse with air stream 74 instead of condensing or poolingin the burner assembly. The particular orifice size to be used in aparticular application will tend to vary with the composition of thefeed stream (or stream of carbon-containing feedstock), the flow rate ofthe stream, and the delivery pressure of the stream. As an illustrativeexample, for a feed stream containing methanol and water in theabove-discussed mix ratio flowing at a feed rate of 15-20 mL/min and apressure in the preferred range presented above, an orifice 100 havingan opening in the range of 0.001-0.015 inches, and more preferably0.006-0.007 inches, in diameter has proven effective.

In FIG. 13, orifice 100 is illustrated schematically as forming part ofthe boundary of ignition region 86 through which stream 78 must passbefore reaching ignition source 88. Another example of a suitableconfiguration for orifice 100 is a nozzle 102 that optionally extendsinto region 86 and includes orifice 100, such as shown in FIG. 14.Regardless of the configuration or placement of orifice 100, it ispreferable that the orifice be preceded with a filter 106, asschematically illustrated in FIGS. 13 and 14. Filter 106 is sized toremove from stream 78 particulate that is large enough to clog orifice100. Filter 106 may be located at any suitable location upstream fromorifice 100.

FIGS. 13 and 14 also demonstrate that it may be preferable for theatomized feed stream 78′ and air 74 to be introduced into ignitionregion 86 at generally intersecting orientations to promote mixing ofthe streams as, or prior to, the streams being ignited by ignitionsource 88. The amount of heat provided by feed stream 78 will increaseas the percentage of the feed stream that is fully combusted increases.One mechanism for increasing this value is to orient the streams orotherwise include structure within the burner assembly that promotesturbulence, and thus mixing, of the gas streams.

In FIG. 14, ignition source 88 is located near the point of intersectionof atomized feed stream 78′ and air stream 74. While effective forigniting the streams, for at least some ignition sources, it may bedesirable for the ignition source to be positioned within assembly 80 sothat it is not in the direct, or at least primary, combustion (flame)region. An example of such a configuration is shown schematically inFIG. 15, in which ignition source 88 is located away from the region atwhich the streams intersect. Another example of such a position is shownin dashed lines in FIG. 15. Because these illustrative configurationslocate the ignition source away from a position where they will be inthe direct flame as the streams are burned, the ignition source will notbe exposed to as high of temperatures as if the source was located in aregion of direct flame. FIG. 15 also graphically illustrates thatignition region 86 may have an outlet 108 for heated exhaust stream 66that has a smaller cross-sectional area than the ignition region.Expressed in other terms, the ignition region may promote greater mixingand combustion of the atomized feed stream and the air stream byrestricting the size of the outlet through which the gases may exit theignition region after combustion has been initiated.

As somewhat schematically illustrated in at least FIGS. 13-15, the fueland air streams are introduced into the ignition region via input ports,or delivery conduits, which are indicated at 101 and 103, respectively.The illustrative examples of the delivery conduits demonstrategraphically that the conduits include at least one opening or orificethrough which the fluid contained therein is released into the ignitionregion, with the conduits terminating at the boundary of the ignitionregion, or optionally, extending into the ignition region. It is withinthe scope of the disclosure that any suitable delivery conduits may beused, and that burner assemblies 80 according to the present disclosuremay include more than one of conduits 101 and 103, with the burnerassemblies thereby being adapted to receive and combust more than onefuel and/or air stream.

Another example of a suitable atomization assembly 94 is an impingementmember 110, as schematically illustrated in FIG. 16. In such anembodiment, stream 78 is delivered under pressure into the ignitionregion such that the pressurized liquid stream strikes the impingementmember 110, where it is atomized and produces an aerosol stream 78′ asit ricochets from the surface. In FIG. 16, member 110 has a contactsurface 112 that extends generally transverse the direction of flow ofstream 78. However, it should be understood that it is within the scopeof the invention that member 110 may have other configurations relativeto the feed stream. FIG. 16 also graphically illustrates that theignition region may include one or more baffles or other suitableturbulent-promoting structures 114.

Other examples are shown in FIG. 17 and include an impingement member110 with a contact surface 116 that extends at an angle in the range of15-75° relative to the direction at which feed steam 78 flows intocontact with the surface. At 118, an example of a non-planar contactsurface for impingement member 110 is shown. Surface 118 tends toproduce a greater dispersion pattern, or a more random dispersionpattern than a planar impingement member, and thereby tends to creategreater turbulence in the stream. At 120, FIG. 17 depicts that a wall ofthe ignition region may itself form an impingement member. In FIG. 18,an impingement member 110 with a non-static contact surface 122 isshown. By this, it is meant that surface 122 is configured to rotate,pivot or otherwise move as it is impacted by the pressurized feedstream. For example, surface 122 may include fins or other contactsurfaces 124 that are rotatably mounted on an axis 126, about which thesurfaces rotate as they are acted upon by feed stream 78 and/or the gasstreams flowing within region 86.

Another example of a burner assembly 80 according to the presentinvention is shown in FIGS. 19 and 20. As shown in FIGS. 19 and/or 20,the burner assembly includes an ignition region 86 with an ignitionsource 88 that is positioned away from the primary region in which theatomized feed stream is mixed with air stream 74. Described in otherwords, the ignition source, which in FIGS. 19 and 20 takes the form of aspark plug, is positioned against a wall of the ignition region, whilefeed stream 78 is delivered to the region approximately in the center ofthe region relative to the ignition source. The burner assembly of FIGS.19 and 20 also demonstrates an atomization assembly 94 that includes anozzle 102 with a reduced-diameter orifice 100, as well as animpingement member 110 with a contact surface 112 positioned to bestruck by feed stream 78 as the feed stream is delivered under pressureinto the ignition region. As also shown, air stream 74 is delivered atan angle to the region. As shown, the air stream is oriented to promoteswirling, and thus mixing, within the ignition region.

Another burner assembly 80 according to the invention is shown in FIGS.21 and 22 and demonstrates an example of a burner assembly that isadapted to receive a liquid fuel stream (which in some embodiments isfeed stream 78 and in others is carbon-containing feedstock 76), as wellas a gaseous fuel stream, such as (but not limited to) byproduct stream28. As perhaps best seen in FIG. 21, the illustrated burner assemblyalso demonstrates a valve assembly 96 that selectively apportions feedstream 78 to form a feed stream 16 for the hydrogen-producing region ofthe associated fuel processor, and/or to form a fuel stream 82 for theburner assembly. Another valve assembly 96′ is also shown selectivelyregulating the flow of byproduct stream 28 to the burner assembly. Whileit is within the scope of the disclosure that the valve assembly may bemanually actuated and/or controlled, it is preferable that the burnerassembly and associated fuel processor include a computerized, orotherwise automated controller 98, such as is shown in FIG. 21communicating with the valve assemblies via communication linkages 128,which may be any suitable form of communication line for control signalsor any suitable mechanical linkage.

It is within the scope of the disclosure that burner assembly 80 islocated external and spaced-apart from an associated fuel processor, inwhich case heated exhaust stream 66 is delivered to the fuel processorvia suitable gas transport conduits, which preferably are insulated toreduce the heat loss during transfer of the exhaust stream. Typically,the burner assembly will be directly coupled to the fuel processor, andoptionally at least partially contained within the shell or otherhousing of the fuel processor. In FIGS. 21 and 22, a mounting plate isshown at 130. Plate 130 is configured to be secured to the fuelprocessor to position and retain the burner assembly in an operativeposition therewith. Plate 130 may be welded to the fuel processor orotherwise secured thereto by another mechanism for fixedly securing theburner assembly to the fuel processor. By “fixedly securing” and“fixedly secured,” it is meant that although it is possible to removethe plate, the fastening mechanism is not intended to be repeatedlyremoved and replaced, and commonly will be damaged during removal.Alternatively, a selectively removable fastening mechanism, such asbolts, threaded fittings, etc. may be used. By “selectively removable”and “removably received,” it is meant that the fastening mechanism isdesigned to be repeatedly removed and reconnected.

Another burner assembly 80 according to the present disclosure is shownin FIG. 23. Similar to the burner assembly shown in FIGS. 21 and 22, theburner assembly of FIG. 23 is also adapted to receive byproduct stream28 or another gaseous combustible fuel, such as to be used as anauxiliary fuel source to supplement, or in some applications, replacethe fuel stream comprised of carbon-containing feedstock 76, and moretypically feed stream 78. In FIG. 23, ignition source 88 is againillustrated as a spark plug, with the spark plug coupled to the burnerassembly by an igniter mount 132. As positioned in FIG. 23, the sparkplug is positioned beneath the level at which the atomized feed streamis introduced into the ignition region. Accordingly, the spark plug issheltered from much of the heat that would otherwise be transferred tothe spark plug if it was mounted within a region of the burner assemblywhere it was generally continuously within the flame produced as thefeed and/or byproduct streams are combusted.

FIG. 23 also demonstrates a distribution plate 140 that is adapted topromote the turbulent mixing of byproduct stream 28 and air stream 74.As shown, the air stream is introduced into a chamber 142 on theopposite side of the plate as the orifice 100 of atomization assembly94, which as shown includes a nozzle 102. In FIG. 23, atomizationassembly 94 has been illustrated as a removable nozzle 102 that isthreadingly received within a socket 143; however, it should beunderstood that any other suitable atomization member, such as thosedescribed and/or illustrated herein, may be used. As perhaps best seenin FIGS. 24 and 25, air stream 74 is delivered into the ignition regionby a plurality of angularly oriented passages 144. The passages haveoutlets 146 that are oriented to direct the air flow into intersectingpaths, and inlets 148 through which the air in the previously describedand illustrated chamber 142 enters the passages. Although four sets ofintersecting passages are shown in FIG. 24, it should be understood thatthe number of passages may vary, from a single passage to more than foursets of passages. Also shown in FIGS. 24 and 25 are distributionconduits 150 within the plate for delivering byproduct stream 28 tooutlets 152, which are oriented to exhaust the byproduct gas stream inan intersecting path with at least a pair of the air streams, as perhapsbest seen in FIG. 25, in which the intersection is schematicallyillustrated at 154.

It should be understood that the burner assemblies illustrated in FIGS.21-26 are not required to utilize byproduct stream 28. As illustrated,the burner assemblies 80 are configured to receive and use liquid andgas fuel streams. Therefore, if byproduct stream 28 is delivered to theburner assemblies, then the byproduct stream is introduced into theignition region. However, if no byproduct stream is delivered to theburner assemblies, then liquid feed stream 78 (or 82) can still be used.

As discussed previously with respect to FIG. 15, burner assembliesaccording to the present invention may include a reduced-area outlet 108from the ignition region to promote additional mixing and/or combustionor within the ignition region. Similarly, because the combusting gasstreams will be discharged from region 86 from the reduced-area opening,the combustion that occurs within heating chamber 92 will also tend tobe more complete. In FIG. 26, the burner assembly of FIG. 23 is shownincluding an extension sleeve 160 that essentially extends the ignitionregion to provide additional space for combustion and/or mixing to occurbefore the gas stream is discharged into the heating chamber, orcombustion region, 92. In FIG. 26, sleeve 160 is shown as a separatelyformed component from the rest of the housing for the burner assembly.Sleeve 160 may alternatively be integrally formed with other portions ofthe burner assembly's housing, such as shown in the subsequentlydiscussed FIG. 28. As perhaps best seen by comparing FIGS. 26 and 27,sleeve 160 includes a neck 162 with outlet 108, which has a smallercross-sectional area than the regions of ignition region 86 leading tothe outlet.

Although the size of burner assembly 80 may vary within the scope of thedisclosure, it is possible for burner assembly 80 to be relativelycompact and yet still provide sufficient durability (such as forignition source 88), mixing and combustion. For example, when the burnerassembly shown in FIG. 26 is sized to receive 15-20 mL/min of feedstream 78, the ignition region may have an inside diameter ofapproximately 2.19 inches, an outlet 108 with an inside diameter ofapproximately 1.125 inches, a sleeve 160 length of approximately 1.125inches, and an overall burner assembly length (measuring in the generaldirection of flow of feed stream 78) of approximately 3 inches.

In FIGS. 23 and 26, atomization assembly 94 was illustrated as includinga removable nozzle 102 that is threadingly received into a socket withindistribution plate 140. To illustrate that this configuration is but oneof many suitable configurations that are within the scope of theinvention, a variation of this structure is shown in FIGS. 28 and 29. Asshown, the atomization assembly still includes a removable, threadednozzle 102. However, in the burner assembly of FIGS. 28 and 29, thenozzle is adapted to be removably received into a nozzle plug 170, whichis itself removably received into a nozzle sleeve 172 within chamber142.

As discussed, burner assemblies 80 according to the present disclosureare configured to receive a liquid fuel stream that contains acarbon-containing feedstock, and which may also include water, such aswhen the burner assembly and the hydrogen-producing region of theassociated fuel processor utilize the same (or nearly the same) feedstream. A benefit of such a construction is that the a steam reformer orother fuel processor that produces hydrogen gas from water and acarbon-containing feedstock does not need to include more than a singlesupply, if the water and water-soluble liquid carbon-containingfeedstock are premixed. If not, then the fuel processor still onlyrequires a water supply and a carbon-containing feedstock supply. Incontrast, conventional steam reformers with burner assemblies to heatthe reformer require a fuel supply and associated delivery andmonitoring systems for the burner assembly, and this fuel supply isindependent from the fuel supply for the steam reformer.

As an illustrative example, startup of a fuel processor 12 in the formof a steam reformer is discussed below. During startup of a steamreformer or other fuel processor with burner assembly 80, at least aportion (if not all) of feed stream 78 is delivered to the burnerassembly and combusted with air stream 74 to produce a heated exhauststream that is used to heat the steam reformer. When the reformer hasbeen heated to a selected, or predetermined, temperature, then the feedstream may be instantaneously switched to the reforming region insteadof the burner assembly. Alternatively, a gradual transition may be used,in which the steam reformer begins receiving some, and then greater andgreater amounts of the feed stream, while the burner assembly receivesless and less of the feed stream. As hydrogen gas is produced in thereforming region of the steam reformer, and then purified in one or moreseparation regions 24, a gaseous byproduct stream 28 may be produced andmay be delivered to the burner assembly to be used as a fuel stream.Typically, the predetermined temperature at which feed stream 78 beginsto be delivered to the reforming region is less than the selected, orpredetermined, reforming temperature, such as 25-125° C., and moretypically 50-100° C., less than the reforming temperature. One reasonfor this is that the reforming reaction typically yields a resultant, ormixed gas stream, 20 that is hotter than the vaporized feed stream 78′delivered thereto. Therefore, there is a tendency for the reformingregion to increase in temperature as the feed stream is reformed.Therefore, heating the reforming region to above the desired reformingtemperature not only results in waste of fuel, but also may result inthe reformer being overheated.

In some applications, such as most steam reformers in which thecarbon-containing feedstock is methanol, the byproduct stream shouldhave sufficient heating value that burner assembly 80 will not requireany of feed stream 78 to maintain the reformer within its selectedoperating temperatures. However, when other carbon-containingfeedstocks, and especially hydrocarbons, are used, it may be necessaryto either continue to supply the burner assembly with some of feedstream 78 and/or use some of the product hydrogen steam as a fuel streamin order to provide sufficient fuel to maintain the temperature of thereformer.

In FIGS. 30-39, various illustrative examples of fuel processors 12 withburner assemblies 80 according to the present invention are shown. Stillother examples of suitable steam reformers with which burner assembliesaccording to the present invention may be used are disclosed in theabove-incorporated patents and patent applications, as well as in U.S.Provisional Patent Application Ser. No. 60/372,258, which was filed onApr. 12, 2002 and is entitled “Steam Reforming Fuel Processor.” Thecomplete disclosure of each of these references is hereby incorporatedby reference for all purposes. For the purpose of brevity, each of theabove-discussed elements, variants thereof, and optional additionalelements for burner assemblies and fuel processors according to thepresent disclosure will not be indicated and discussed in the followingillustrative examples. For correlational purposes, illustrative ones ofthe reference numerals introduced above have been included in FIGS.30-39; however, and as discussed, each of these numerals is notrediscussed below. It is within the scope of the disclosure that otherburner assemblies described, illustrated and/or incorporated herein maybe used in place of the illustrative examples of atomizing burnerassemblies depicted in FIGS. 30-39. For example, any of the previouslydescribed atomizing burner assemblies or any of the subsequentlydescribed diffusion burner assemblies may be used in place of theillustrative examples depicted in FIGS. 30-39. As discussed, it is alsowithin the scope of the disclosure that the burner assembliesillustrated in FIGS. 30-39 may be utilized in other applications,including in other types and/or configurations of fuel processors.

In FIG. 30, an illustrative fuel processor 12 is shown that is adaptedto produce a mixed gas stream containing hydrogen gas and other gases bysteam reforming a feed stream 16 containing water 17 and acarbon-containing feedstock 76. Steam reforming fuel processor 200,which may be referred to as a steam reformer, includes ahydrogen-producing region 19 that contains steam reforming catalyst 23.As shown, the hydrogen-producing region and atomizing burner assembly 80are adapted to receive feed/fuel streams 82 and 16, respectively, thatcontain water and a carbon-containing feedstock. Fuel processor 200 alsoprovides an illustrative example of a vaporization region 69, in whichfeed stream 16 is vaporized prior to delivery to the hydrogen-producingregion of the fuel processor. Fuel stream 82 is combusted with airstream 74, and the heat produced thereby is used to vaporize the feedstream and to heat the reforming catalyst in the hydrogen-producingregion to a selected reforming temperature, or range of temperatures. Inthe illustrated embodiment, the heated exhaust stream from the burnerassembly flows through passages that extend through thehydrogen-producing region. As shown, reforming catalyst 23 surrounds theconduits containing the heated exhaust stream. It is within the scope ofthe disclosure that other configurations may be used, such as in whichthe reforming catalyst is housed in conduits, or beds, around which theheated exhaust stream passes.

As also indicated in FIG. 30, atomizing burner assembly 80 is alsoadapted to receive the gaseous byproduct stream 28 from separationregion 24, such as may be produced by one or more hydrogen-selectivemembranes 30 that are schematically illustrated in FIG. 30. Asdiscussed, burner assembly 80 (or one of the subsequently describeddiffusion burner assemblies 262) may be adapted to utilize liquid and/orgaseous combustible fuel streams. It is within the scope of thedisclosure that the burner assembly may use one type and/or compositionof fuel stream during some operating states of the fuel processor, suchas during start up of the fuel processor, and other types and/orcompositions of fuel stream during other operating states of the fuelprocessor, such as during a hydrogen-producing state and/or an idle, orstandby, operating state.

FIGS. 31 and 32 depict another example of a fuel processor 12 that isadapted to produce hydrogen gas via a steam reforming reaction. Asshown, the steam reforming fuel processor is generally indicated at 210and is configured to have a vertical orientation, in contrast to theillustrative horizontal configuration shown in FIG. 30. Although notrequired, a benefit of a vertical orientation in which the burnerassembly introduces the heated exhaust stream generally within a chamberor annulus defined by at least the hydrogen-producing region of thesteam reformer is that the reforming catalyst beds (or otherhydrogen-producing region used in other fuel processors within the scopeof the present disclosure) are provided with a thermal symmetry relativeto the heated exhaust stream. As shown, the burner assembly extendsgenerally beneath the hydrogen-producing region of the fuel processorand produces a heated exhaust stream that flows into a combustion region92 that is at least partially surrounded by the hydrogen-producing andvaporizing regions of the fuel processor. The illustrated burnerassembly 80 has the configuration of the burner assembly that waspreviously described with respect to FIGS. 21 and 22. As discussed,however, any of the atomizing and diffusion burner assemblies described,illustrated and/or incorporated herein may be used in place of theillustrated burner assembly.

Reformer 210 provides a graphical example of a fuel processor thatincludes at least one insulated shell 68. As indicated in solid lines,the reformer may be described as including an insulating shell 68 thatencloses at least a substantial portion of the reformer. In theillustrated example, shell 68 defines a compartment into which thehydrogen-producing, vaporization and vaporization regions of the fuelprocessor are housed, with the shell defining an opening 211 to which abase, or mount, for the fuel processor is coupled to the shell. Asshown, shell 68 includes various types of insulating material 70, suchas an air-filled cavity, or passage, 212 and a layer of solid insulatingmaterial 214. The depicted examples of insulating materials areseparated by inner layers of shell 68, although it is within the scopeof the disclosure that other shell and/or insulating configurations maybe used, including fuel processors that do not include an externalshell. As indicated in dashed lines in FIGS. 31 and 32, shell 68 mayalternatively be described as being surrounded by an insulating jacket72, such as with air-filled cavity 212 separating the shell from jacket72.

FIGS. 31 and 32 depict examples of several different types of filtersthat may be used with fuel processors according to the presentdisclosure. For example, at 215 in FIG. 31 a filter is shown positionedto remove particulate or other types of impurities from reformate (mixedgas) stream 20 prior to delivery to separation assembly 24. Also shownin both FIGS. 31 and 32 is an exhaust filter 216 that is adapted toremove selected impurities or other materials from the heated exhauststream produced by the burner assembly before the exhaust stream exitsshell 68, such as through exhaust opening 218. As indicated in dashedlines, one type of suitable exhaust filter is a catalytic converter 220,although others may be used. Also shown in FIGS. 31 and 32 is an orifice221 through which the exhaust stream passes from an inner chamber of theshell.

Similar to the exemplary atomizing burner assembly 80 shown in FIG. 30,the burner assembly shown in FIGS. 31 and 32 is adapted to combust withair (such as from air stream 74) and at least one of a gaseous and aliquid fuel stream. As perhaps best seen in FIG. 31, a common feedstream 78 may be used to supply both a liquid fuel stream 82 to theburner assembly and a reforming feed stream 16 to the hydrogen-producing(steam reforming) region 19 of the fuel processor. In such anembodiment, stream 78 contains both water and a liquid carbon-containingfeedstock. As also shown, the gaseous byproduct stream 28 from aseparation region 24 also may be consumed as fuel for the burnerassembly.

In the illustrated embodiment, the fuel processor utilizes a separationregion that contains at least one hydrogen-selective membrane 30 toseparate the reformate (mixed gas) stream produced in thehydrogen-producing region into a hydrogen-rich stream 26 and a byproductstream 28. As shown, this separation region takes the form of a module,or housing, 225 that defines a compartment 227 into which reformatestream 20 is delivered under pressure and separated into streams 26 and28. In FIGS. 31 and 32, this membrane module utilizes generally planarmembranes 30 that extend generally transverse to the reforming catalystbeds and the central axis of the burner assembly. The feed stream forthe reformer is vaporized in vaporization region 69, which takes theform of a central coil that surrounds at least a portion of combustionregion 92. The vaporized feed stream is distributed to a plurality ofreforming catalyst beds 222 by a distribution manifold 224. Thereformate stream produced in beds 222 is collected in a collectionmanifold 226 and thereafter delivered to an internal compartment 227 ofthe membrane module. At 228, an optional fluid transfer conduit isshown. Conduits 228, which extend generally between upper and lowerportions of the hydrogen-producing region of the reformer may be used tocontrol whether various fluid streams flow generally in the direction ofthe heated exhaust stream (away from the burner assembly) or generallytoward the burner assembly. For example, the selected direction of flowmay be used to control the temperature of the fluid within the stream orthat is delivered to various regions of the reformer. As also shown, aninsulating member, or heat shield, 230 may be used to protect themembrane module from being overheated by the burner assembly. Forexample, in the context of hydrogen-selective palladium-coppermembranes, it is generally preferable (although not required) tomaintain the membranes at a temperature that is less than approximately450° C.

Reformer 200 also provides an example of a fuel processor that includesmore than one type of separation region 24. As shown in FIG. 30, thefuel processor also includes a separation region that includes a carbonmonoxide removal assembly 32, such as a methanation region that containsmethanation catalyst 34, with this second separation region beingpositioned downstream from a separation region 24 that containshydrogen-selective membranes 30. Accordingly, methanation region 34 ispositioned to further purify the hydrogen-rich stream produced by thehydrogen-selective membranes.

In FIGS. 33-39 another illustrative example of a steam reforming fuelprocessor utilizing a burner assembly according to the presentdisclosure is shown and generally indicated at 240. Reformer 240 has asimilar configuration to reformer 210. Reformer 240 is shown including aburner assembly 80 that is similar in configuration to the burnerassembly shown in FIGS. 28 and 29 to provide a graphical example thatthe illustrative reformer may be used with any of the burner assembliesdescribed, illustrated and/or incorporated herein. For the purpose ofcontinuity, many of the above discussed structure and reference numeralsare depicted in FIGS. 33-39. However, each of these structures and/orreference numerals will not be rediscussed below. The illustratedexample of a steam reforming fuel processor includes an optional base,or base plate, 242 having a plurality of supports, or legs, 246. Severaloptional sensors 254 are also illustrated.

Reformer 240 provides a graphical illustration that the steam reformersand other fuel processors with burner assemblies according to thepresent disclosure may include heat distribution structure that isadapted to normalize, or even out the temperature distribution producedby the heated exhaust stream from the burner assembly in the combustionregion. In this region, even when there is thermal symmetry of thevaporization region and/or hydrogen-producing region, it is possiblethat “hot spots” or localized regions of elevated temperature mayoccasionally occur within the combustion region and/or vaporizationregion. As shown in FIGS. 34 and 37-39, reformer 240 includes a pair ofheat diffusion structures 250 and 252. Structure 250 is adapted toreduce and/or dissipate these hot spots as heat is transferred fromcombustion region 92 to vaporization region 69. Diffuser 250 is adaptedto provide a more even temperature distribution to vaporization region69 than if the diffuser was not present. Because the diffuser willconduct and radiate heat, hot spots will tend to be reduced intemperature, with the heat in hotter areas distributed to surroundingareas of the diffuser and surrounding structure. An example of asuitable material for diffuser 250 is FeCrAlY or one of the otheroxidation-resistant alloys discussed above.

In embodiments of reformer 240 (or other fuel processors) that include adiffuser, a suitable position for the diffuser is generally between thevaporization region and the heating assembly, as indicated with diffuser250 in FIGS. 34 and 37-39. The diffuser typically will extend at leastsubstantially, if not completely, around the vaporization region and/orthe heating assembly. Another suitable position is for the diffuser tosurround hydrogen-producing region 19, as illustrated at 252. It iswithin the scope of the disclosure that one or more diffusers may beused, such as in an overlapping, spaced-apart and/or concentricconfiguration, including a reformer that includes both of theillustrative diffuser positions shown in FIGS. 34 and 37-39.

In the illustrative configurations shown in FIGS. 34 and 37-39, theplurality of reforming catalyst beds 222 may be described ascollectively defining inner and outer perimeters, with the diffuserextending at least substantially around at least one of the inner and/orthe outer perimeters of the plurality of reforming catalyst beds. Atleast diffuser 250 should be formed from a material through which thecombustion exhaust may pass. Examples of suitable materials includewoven or other metal mesh or metal fabric structures, expanded metal,and perforated metal materials. The materials used should be ofsufficient thickness or durability that they will not oxidize orotherwise adversely react when exposed to the operating parameterswithin reformer 240. As an illustrative example, metal mesh in the rangeof 20-60-mesh has proven effective, with mesh in the range of 40-meshbeing preferred. If the mesh is too fine, the strands forming thematerial will tend to oxidize and/or will not have sufficientheat-conducting value to effectively diffuse the generated heat.

As discussed herein, steam reformers and other fuel processors withburner assemblies according to the present disclosure will often be incommunication with a controller that regulates the operation of at leasta portion of the burner assembly and/or the entire fuel processor, fuelprocessing system, or fuel cell system responsive to one or moremeasured operating states. An example of a suitable controller for asteam reforming fuel processor is disclosed in U.S. Pat. No. 6,383,670,the complete disclosure of which is hereby incorporated by reference forall purposes. Accordingly, the reformers may include various sensors254, such as temperature sensors, pressure sensors, flow meters, and thelike, of which several illustrative examples are shown in FIGS. 34-39.

Also shown in FIGS. 34-35 and 37-38 is an optional evaporator 256 thatis adapted to vaporize any residual liquid-water content in exhauststream 66. In many embodiments, evaporator 256 will not be necessary.However, in some embodiments, additional fluid streams are mixed withthe exhaust stream external hydrogen-producing region 19 to reduce thetemperature of the resulting stream. As an example, the cathode airexhaust from a fuel cell stack may be mixed with stream 66. This airexhaust stream has a vapor pressure of water that exceeds the stream'ssaturation point. Accordingly, it contains a mixture of liquid water andwater vapor. To prevent water from condensing or otherwise depositingwithin the reformer or other fuel processor, such as on separationregion 24, evaporator 256 may be used.

Another burner assembly 62 according to the present disclosure isschematically illustrated in FIG. 40 and generally indicated at 262. Asshown, burner assembly 262 includes a diffusion region 270 in which acombustible fuel stream 64 is mixed with an air stream 74 to form anoxygenated combustible fuel stream 74. Therefore, and in contrast toburner assemblies that receive premixed streams of fuel and oxidant,burner assemblies according to at least this aspect of the presentdisclosure receive at least one combustible fuel stream and at least oneair/oxygen stream, and then mix these streams in diffusion region 270.Although described herein as an air stream 74, it is within the scope ofthe disclosure that stream 74 may have a greater oxygen content thanair, that the stream may be otherwise depleted in components present inair, enriched in one or more of these components, and/or contain one ormore components that are not normally present in air. In the illustratedembodiment, the fuel stream is a gaseous combustible fuel stream 276.

Diffusion region 270 includes diffusion structure 278 that is adapted topromote the formation of one, and typically a plurality of, oxygenatedcombustible fuel streams 274, as schematically indicated in FIG. 40. Theoxygenated combustible fuel stream, which may also be referred to as theoxygenated fuel stream is then delivered to a combustion region 92,where it is ignited to produce a heated exhaust stream 66, which mayalso be referred to herein as a combustion stream 66. Combustion region92 includes at least one ignition source 88, which is adapted to ignitethe oxygenated fuel stream. Ignition source 88 may optionally bedescribed as being within an ignition region 86 within the combustionregion. An example of a suitable diffusion structure 278 is a structurethat promotes mixing of the gaseous streams into a relatively uniformmixture of air/oxygen and gaseous fuel. The resulting stream 274 willtend to burn cleaner and more efficiently than if the diffusionstructure is not present.

As shown in FIG. 41, burner assemblies 262 according to the presentdisclosure may additionally or alternatively include a distributionregion 284, in which at least one of the air and/or fuel streams isdivided into a plurality of smaller streams. Accordingly, distributionregion 84 includes distribution structure 86, which is adapted toreceive and divide at least one of the fuel and air streams into aplurality of smaller streams. Although not required, burner assemblies262 that receive a primary air stream and a primary fuel streampreferably include distribution regions 284 that are adapted to receiveand divide each of these streams into a plurality of smaller streams.This is schematically illustrated in FIG. 41, where air stream 74 isdivided into a plurality of smaller air streams 74, and fuel stream 276is divided into a plurality of smaller fuel streams 276′. As shown,streams 72′ and 276′ are mixed in diffusion region 270 to produce aplurality of oxygenated fuel streams 274, which are ignited incombustion region 92. As used herein in the context of the flows offluid streams, “smaller” refers to the mass/molar flow rate of thestreams compared to the corresponding mass/molar flow rate of theprimary stream.

An example of a suitable distribution structure 286 is structure thatsubdivides the air and combustible fuel streams into a plurality ofsmaller streams that are delivered in pairs or other groupings of atleast one of each subdivided stream to an ignition source. Thisconfiguration provides cleaner, more efficient combustion of theoriginal fuel stream because the overall flow of the fuel stream isdivided into smaller streams that are mixed with one or morecorresponding air streams. This configuration enables better overalldiffusion, or mixing, of the streams and enables combustion to becompleted with a smaller flame than a comparative burner assembly inwhich the fuel and oxidant streams are not divided prior to combustion.As indicated in dashed lines in FIG. 41, distribution region 284 ispreferably configured to divide the fuel and air streams without mixing,or enabling diffusion, of the streams. Therefore, although illustratedschematically as a single box in FIG. 41, the distribution region may beimplemented as separate regions for the air and the fuel streams and/ormay include distribution structure that is adapted to maintain the fueland air streams separate from one another until the smaller streams aredelivered to diffusion region 270.

Burner assemblies 262 according to the present disclosure mayadditionally or alternatively be configured to receive a combustiblefuel stream 64 in the form of a liquid combustible fuel stream 82.Illustrative, non-exclusive examples of liquid combustible fuel streams82 include streams that contain as at least a majority component one ormore liquid alcohols or hydrocarbons. An example of such a burnerassembly is schematically illustrated in FIG. 42. As shown, fuel stream82 is delivered to a vaporization region 92, in which the stream isvaporized to form a vaporized fuel stream 294. The vaporized fuel streamis delivered to distribution region 284, where it is divided into aplurality of smaller fuel streams 294′. As shown, distribution region284 also receives air stream 74 and divides the air stream into aplurality of smaller air streams 74′. Streams 74′ and 294′ are deliveredto diffusion region 270, where they are mixed in selective pairs orsimilar groupings to produce a plurality of oxygenated fuel streams274′.

FIG. 42 also graphically illustrates in dashed lines that burnerassemblies 262 according to the present disclosure may additionally oralternatively be configured to receive and combust both liquid andgaseous combustible fuel streams 82 and 276. In embodiments where theburner assembly also receives a combustible gaseous fuel stream 276,streams 294, 294′ and 274′ will contain both vaporized and gaseouscombustible fuels.

As shown in FIG. 42, the burner assembly includes a vaporizing heatingassembly 296 that is adapted to heat the vaporizing region to vaporizethe liquid combustible fuel stream. Also shown in FIG. 42 is a fuelstream 298 for the vaporizing heating assembly. Stream 298 will tend tovary in composition and/or form depending upon the particular structureof vaporizing heating assembly 296. For example, when assembly 296 isadapted to combust a combustible fuel stream, then stream 298 willcontain such a stream. Similarly, when assembly 296 is an electricallypowered heating assembly, then stream 298 will include an electricalconnection to a power source (including, but not required to be orlimited to, fuel cell stack 40 and/or battery 52).

For purposes of illustration, the components of the burner assembliesshown in FIGS. 40-42 have been illustrated as being spaced-apart fromeach other, with the corresponding streams being delivered between thesecomponents. Although not required, actual burner assemblies willtypically have at least one, if not all of these components housedtogether within, and/or collectively define, a common shell or housing.For example, the entire burner assembly may be contained within a shellor housing. As another example, two or more of the burner assemblies'functional regions may be integrated or otherwise contained within acommon shell or housing. As an illustrative example of this alternative,the diffusion and combustion regions may be integrated together so thatthe air and fuel streams are separately introduced into the combustionregion, but introduced in a manner that promotes diffusion of thestreams as they are introduced and ignited.

FIG. 43 provides a less schematic example of a diffusion burner assembly262 according to the present disclosure. As shown and generallyindicated at 300, the burner assembly is configured to receive gaseousand/or liquid combustible fuel streams 64 through respective gas andliquid input ports 302 and 304. Although only a single one of each portis shown in FIG. 43, it is within the scope of the disclosure that twoor more of each port may be used. When burner assembly 300 is adapted toreceive both liquid and gaseous fuel streams, the burner assembly willtypically be installed with each port connected via suitable conduits torespective supplies from which the fuel streams are obtained. When theburner assembly is adapted to receive only a gaseous or only a liquidfuel stream, one of the ports may be eliminated, blocked, or otherwisenot functionally present in the burner assembly.

As shown in FIG. 43, liquid stream 82 is delivered to vaporizationregion 292, where it is vaporized and forms vaporized fuel stream 294,such as by heat provided by vaporizing heating assembly 296. Instead ofbeing delivered as a single vaporized gas stream to combustion region 92(with or without premixing of air), the vaporized gas stream must passthrough distribution region 284, where distribution structure 286divides the vaporized fuel stream 294 into a plurality of streams 294′.Furthermore, streams 294′ are then mixed through diffusion with acorresponding plurality of air streams 74′, and the resulting oxygenatedfuel streams 274′ are combusted to collectively produce hot combustionstream 66. Therefore, burner assembles 262 according to the presentdisclosure are configured to receive combustible fuel and air streams,and divide these streams into a plurality of streams that each containonly a minority, and often 10% or less, of the original flow. Thesmaller streams are then mixed, ignited, and recombined to formcombustion stream 66.

As shown in FIG. 43, distribution structure 286 includes a fueldistribution manifold 310, which includes a plurality of fuel apertures312 into which the vaporized fuel stream may flow into a correspondingplurality of fuel tubes 314. In the illustrated embodiment, apertures312 define the inlets to tubes 314. As shown, the tubes are spaced-apartfrom each other and extend from manifold 310 to combustion region 92,where the tubes terminate at outlets 316 from which the fuel streams aredelivered into the combustion region. Therefore, instead of receiving asingle vaporized fuel stream with a flow rate that is at leastapproximately equal to the flow rate of the original liquid fuel streamthat was delivered to vaporization region 292, the combustion regionreceives a plurality of vaporized fuel streams that each contain only aminority fraction of the original flow. For example, each stream maycontain 25% or less of the original flow. It is within the scope of thedisclosure that each stream may contain less than 20%, less than 15%,less than 10%, less than 5%, between 1-10%, or between 2-5% of theoriginal flow. It should be understood that the percentage of theoriginal flow that passes through the individual tubes is largelydependent upon the number of such tubes that are present and availableto receive the vaporized fuel stream. Accordingly, it should also beunderstood that the number of tubes shown in FIG. 43 has been selectedfor representation purposes only and that the actual number may vary,such as depending upon one or more of the desired flow rate through eachtube and the desired proportion of the total flow desired through eachtube.

The number and size of tubes 314 is preferably, but not required to be,selected to maintain the flow velocity of the combustible fuel passingthrough the tubes to be below the flame-front velocity of the particularfuel. By this it is meant that the combustible fuel streams preferablyare not flowing at such a velocity, or fluid flow rate, that the flameslift off of the outlets 316 of the tubes. For purposes of illustration aflame is shown in FIG. 43 at 318. As shown, the flame may be describedas being attached to outlet 316 because combustion is initiated at theoutlet, as opposed to at a region spaced above the outlet. This latter,less desirable situation is schematically illustrated in FIG. 44 at318′. Flame 318′ tends to be less stable than flame 318, and will oftenresult in less efficient combustion and a less uniform flame. As such,the flame is more likely to flameout and may also impinge againstadjacent structure that would not be impinged against by flame 318. Thisimpingement may produce undesirable combustion byproducts, lower theheating value of the combustible fuel stream, and/or damage or weakenthe impinged upon structure. Although tubes 314 are shown in FIGS. 43and 44 as having right cylindrical configurations, it is within thescope of the disclosure that other cross-sectional and lengthwiseconfigurations may be used. Similarly, stainless steel tubes have proveneffective in experiments, but it is within the scope of the disclosurethat any other suitable material may be used. Preferably the tubes arenot configured so that the vaporized fuel stream is cooled to the pointof condensing, as the condensed liquid may obstruct the tubes andprevent further passage of vaporized fuel therethrough.

Preferably, each tube 314 forms a portion of manifold 310 or isotherwise in fluid communication therewith such that any gas passingthrough one of apertures 312 passes into the tube and cannot flow intothe subsequently described air distribution chamber 322. Fueldistribution manifold 310 may, in at least some embodiments, be referredto as a distribution plenum, in that it maintains the pressure withinvaporization region 292 at least slightly greater than the pressure inthe plurality of fuel tubes. This pressure differential promotesdistribution of the vaporized fuel stream between the tubes, and inembodiments where both gaseous and vaporized fuel streams are present invaporization region 292, promotes mixing of the streams withinvaporization region 292.

When burner assembly 300 receives a gaseous combustible fuel stream 276in addition to liquid combustible fuel stream 82, the gaseous fuelstream is also delivered to the vaporization region, where it mixes withthe vaporized fuel stream and the resultant stream is distributedbetween the fuel tubes. This is schematically illustrated in dashedlines in FIG. 43, where the tubes are shown including streams 294″,which contain both gaseous and vaporized combustible fuels. It is withinthe scope of the disclosure that the gaseous and vaporized fuel streamsmay be only partially mixed prior to entering the fuel tubes and thatfurther mixing or diffusion of the streams may occur within theindividual fuel tubes. Similar to the above discussion of the flow ratesof streams 294′, it should be understood that each of the streams 294″will include a minority fraction of the original flows of the liquid andgaseous combustible fuel streams, with the above-described illustrativepercentages being again applicable.

As discussed, the burner assembly additionally or alternatively may beimplemented or configured so that it only receives a gaseous combustiblefuel stream 276. In such an application or implementation, thevaporization region may be referred to as a staging region, in that thegaseous combustible fuel stream is delivered into the region and thendivided into a plurality of smaller streams 276′ by fuel distributionmanifold (or plenum) 310.

Burner assembly 300 also includes at least one air input port 320through which air stream 74 is delivered into distribution region 284.As shown in FIG. 43, the air stream is delivered into an airdistribution chamber 322 in which the air may flow around the pluralityof fuel tubes. As also shown in FIG. 43, the distribution structureincludes a combustion distribution manifold 324. Manifold 324 is adaptedto divide the air stream 74 that is delivered into chamber 322 into aplurality of air streams 74′, with each stream 74′ containing only aminority fraction of the original air stream. For example, each streammay contain 25% or less of the original flow. It is within the scope ofthe disclosure that each stream may contain less than 20%, less than15%, less than 10%) less than 5%, between 1-10%, or 2-5% of the originalflow. In at least some embodiments of the burner assembly, combustiondistribution manifold 324 may be referred to as a combustion plenum, inthat it maintains the pressure within chamber 322 at least slightlygreater than the pressure within combustion region 92. This pressuredifferential promotes the even flow of air into the combustion regionand restricts the flow of the fuel streams into the air distributionchamber.

As shown in FIG. 43, manifold (or plenum) 324 includes a plurality ofapertures 326 through which air streams 74′ flow into the combustionregion. As also shown, the apertures are sized so that tubes 314 mayextend into, and in the illustrated embodiment through, the apertures.As shown, the tubes are concentrically located within apertures 326 sothat each fuel stream (such as 276′, 294′ or 294″) is surrounded by acorresponding air stream 74′ as it exits the corresponding tube 314. Aseach fuel stream exits its corresponding tube 314, it is mixed throughdiffusion with the surrounding air stream 74′ to produce an oxygenatedfuel stream 274′, which is ignited, such as by ignition source 86. Assuch, the region in which the air and fuel streams are diffused togethermay be referred to as the diffusion region of the burner assembly, withthe configuration of outlets 316 and apertures 326 providing thediffusion structure, which enables the pairs of air and fuel streams todiffuse together. The hot combustion gases produced from the pluralityof streams 274′ collectively form a hot combustion stream 66.

The distribution of the combustible fuel and air streams into aplurality of smaller, and optionally concentric, streams enables theburner assembly to complete combustion of the fuel streams with asmaller flame than otherwise would be obtained if the original streamswere not divided. As the number of tube and aperture assemblies isincreased for a fixed feed of fuel/air, the proportional flow througheach tube decreases. As such, the distance required for completediffusion and combustion of the fuel delivered by that assembly willtend to be reduced. For example, the subsequently described andillustrated burner assembly shown in FIGS. 45-50 is adapted to completecombustion of combustible fuel delivered at a flow rate of 60 mL/minwithin 6 inches, and more commonly within approximately 4 inches ofoutlets 316.

Similar to the above discussion about the velocity at which theplurality of fuel streams are delivered to the diffusion and combustionregions, air streams 74′ are also preferably delivered to the diffusionand combustion regions at velocities that do not cause or promoteflameout or separation of the flames from outlets 316. It should beunderstood that the size of apertures 326 may be selected to provide thedesired mass/molar flow of oxygen without producing an undesirablevelocity for the air stream.

Preferably, air streams 74′ are delivered so that at least thestoichiometric amount of oxygen required for complete combustion isdelivered to each combustible fuel stream. For example, a liquidcombustible fuel stream that contains a mixture of approximately 70% (byvolume) methanol and the balance water stoichiometrically requiresapproximately 40 L/min air. Preferably, and to provide an excess, orbuffer, of oxygen, more than the stoichiometrically required amount ofoxygen is delivered. For example, the oxygen in streams 74′ may bepresent at greater than approximately 1, 2, 3 or more times thestoichiometrically required amount of oxygen for a particularcomposition of combustible fuel. An air stream 74′ that contains anoxygen component that is present in the range of 1.1-1.3 times thestoichiometrically required amount of oxygen has proven effective, butother oxygen flow rates that are above and below this amount may be usedand are within the scope of the disclosure.

Burner assemblies 262 constructed according to the present disclosuremay be effectively utilized with several times the stoichiometricallyrequired amount of oxygen. For example, when 200-500% excess air isdelivered to the burner assembly, the burner assembly still effectivelycombusts the fuel streams and produces a hot combustion stream. Theimpact of this excess air is that the flame will be cooler, or in otherwords, hot combustion stream 66 will not be as hot as a comparativestream produced with less excess air. The amount of excess air providesa mechanism by which the amount of heat produced by the burner assemblymay be controlled by controlling the rate at which air is delivered tothe burner assembly. As discussed above, when it is envisioned that theburner assembly will be utilized in such an excess air configuration,apertures 126 may be sized so that the resulting streams 74′ of excessair do not travel at sufficient velocities to cause flameout, andpreferably are sized so that the flames are not separated from outlets316.

In the embodiment illustrated in FIG. 43, each fuel tube 314 extendsthrough one of apertures 326 in combustion manifold 324. In thisconfiguration for diffusion structure 278, the portion of air stream 74that passes through each aperture 326 produces an airflow that surroundsthe respective outlets of the fuel streams. A benefit of such aconfiguration is that the combustible fuel stream is delivered abovecombustion manifold 324, thereby reducing the chance that thecombustible fuel will flow into the diffusion region external the tubes.It is within the scope of the disclosure, however, that one or more ofthe fuel tubes may have outlets 316 that are co-terminus with thecombustion- or distribution-faces (330 and 332, respectively) ofcombustion manifold 324, anywhere in between, or even that the tubesterminate prior to reaching manifold 324. Because the air stream isdelivered into the distribution region external the tubes and cannotflow into vaporization region 292, the air stream will create a positiveflow of gas from distribution region 284 to the diffusion and combustionregions 270 and 92. Examples of several of the above-describedvariations are graphically illustrated in FIG. 44. As shown, tubes 314on the left side of FIG. 44 do not extend beyond the combustion-surface330 of manifold 324, and the tubes 314 on the right side of FIG. 44terminate generally between the combustion- and distribution-surfaces332 and 330 of manifold 324.

As discussed, burner assemblies 262 according to the present disclosuremay be configured to receive only one of a gaseous or a liquidcombustible fuel stream. In embodiments or applications where only agaseous combustible fuel stream is received, it should be understoodthat heating assembly 96 is not required. In fact, when the burner isconfigured to only receive gaseous combustible fuel streams, the burnerassembly may be formed without the vaporizing heating assembly, as shownon the left side of FIG. 44. When the burner assembly is selectivelyused with either or both of the above fuel streams, the burner assemblywill tend to be present, but will generally not be used when only agaseous fuel stream is received into the vaporization region.

On the right side of FIG. 44, several optional configurations are shownfor vaporization region 292 and the corresponding vaporizing heatingassembly 296 of burner assemblies that are configured to receive aliquid combustible fuel stream, either alone or in addition to a gaseouscombustible fuel stream 276. As shown, vaporization region 292 includesa base 340 and a partition 342 that extends from the base generallytoward fuel distribution manifold 310. Partition 342 creates a well, orreservoir, 344 into which liquid combustible fuel stream 82 is initiallydelivered upon introduction into the vaporization region. Reservoir 344enables a volume of liquid combustible fuel stream 82 to be deliveredinto the vaporization region and to pool or accumulate, in thereservoir. The level of the pooled stream will rise until it reaches theheight of the partition, at which point the delivery of an additionalamount of stream 82 will cause some of the stream to pour over thepartition. When this occurs, then at least the portion that pours (orspatters) over the partition will contact the region 352 of base 340that does not extend under reservoir 344, where it is vaporized by heatprovided by heating assembly 296.

A benefit of this configuration is that the burner assembly has a“reserve” or “buffer” 346 of liquid combustible fuel. For example,should the flow rate of stream 82 to burner assembly 300 be interruptedor otherwise non-uniform, the reserve can be vaporized as it is heatedto maintain a flow of vaporized fuel to the combustion region. While theflow of vaporized fuel from the reservoir when no new liquid combustiblefuel is being delivered to the reservoir may be less than thecorresponding flow that would be produced if stream 82 was uniformlydelivered to the burner assembly, it still provides a mechanism by whichthe flame created in combustion region 92 is less likely to beextinguished. Therefore, the reservoir may be described as a mechanismfor leveling, or equalizing, the flow of combustible fuel to combustionregion 92 relative to the rate at which it is delivered to vaporizationregion 292. A benefit of this construction is that unstable delivery ofcombustible fuel to the combustion region may cause flameouts, such aswhen there is no flow of combustible fuel or a period of low flowfollowed immediately by a period of much greater flow. Even when thesefluctuations do not cause the flame to be completely extinguished, theywill still tend to cause instability in the flame, such as flare-ups andperiods of incomplete combustion. Therefore, burner assemblies with thestructure shown in FIG. 44 are less likely to encounter flameout, orunstable combustion, situations than conventional liquid-fuel burnersthat do not have this structure.

As a variation of the above construction, partition 342 may include oneor more ports, channels or similar conduits 348 therethrough thatenables some of the liquid combustible fuel stream to flow through thepartition. Preferably, the conduit or conduits are sized such that theflow rate of combustible liquid fuel that flows through the conduits perunit time is not greater than the flow rate of stream 82 into thevaporization region. In other words, when partition 342 includes one ormore conduits 348, stream 82 is preferably delivered into thevaporization region at a flow rate that exceeds the rate at which theliquid fuel flows through the one or more conduits 348. In thisconfiguration, a reserve of liquid fuel will be established andcontinuously replenished as long as the flow of stream 82 is notinterrupted or diminished for a sufficient time that the reserve ofliquid fuel is depleted, such as by flowing through the partition and/orbeing vaporized. However, as long as the reservoir contains a supply ofliquid fuel that may flow through the partition and be vaporized, thenet flow of vaporized fuel to distribution region 284 will becomparatively stable or normalized, even if the flow rate of stream 82tends to vary over time.

For example, one suitable mechanism for delivering stream 82 tovaporization region 292 is to use a pump. Some pumps, such asreciprocating piston pumps, deliver liquid in intervals (such as duringhalf of each piston cycle) and therefore do not provide a constant flowof stream 82. Accordingly, a reciprocating piston pump will tend todeliver flows of stream 82 in intervals, and the use of partition 342(with or without conduit(s) 348) can stabilize or normalize the flow ofvaporized fuel produced therefrom.

As indicated at the bottom of FIG. 44, it can be seen that thevaporization heating assembly may be configured to heat the entire base340 of the vaporization region, including the portion of the base thatunderlies reservoir 344. A benefit of this construction is that all ofthe liquid fuel stream will be eventually vaporized by the vaporizingheating assembly. An alternative configuration is schematicallyillustrated in dashed lines. In this alternative configuration, thevaporization heating assembly is adapted to either not directly heat theportion 350 of the base beneath the reservoir, or to not heat thatregion to as high of temperature as the portion 352 of the base uponwhich the liquid combustible fuel stream is intended to be vaporized.For example, the vaporization heating assembly may be located generallybeneath only portion 352. Expressed in different terms, the reservoirmay be offset or otherwise located distal the heating assembly. As anadditional or alternative implementation, portion 350 may be insulatedor formed from a material which is not as conductive as the materialfrom which the rest of the base is formed.

Another burner assembly 262 constructed according to the presentdisclosure is shown in FIGS. 45 and 46 and generally indicated at 400.As used herein, similar elements and subelements will retain the samereference numerals between the various illustrative embodiments of theburner assemblies, fuel processing and fuel cell systems disclosedand/or illustrated herein. It is within the scope of the disclosure thatthese later-referenced structures may (but are not required to) have thesame elements, subelements and variations as the earlier presentedstructure. As an illustrative example, burner assembly 400 includes avaporization region 292 with a partition 342. However, and similar topreviously discussed embodiments, it is within the scope of thedisclosure that burner assembly 400 may be formed without a reservoirand/or with a reservoir that includes one or more conduits 348 thatextend through the partition. As another example, although the fueltubes shown in FIG. 46 extend through combustion distribution manifold324, it is within the scope of the disclosure that the tubes may haveany of the other relative positions) geometries and the like that areillustrated and/or described herein. For the purpose of simplifying thedrawings, every subelement and/or optional structure will not berepeatedly discussed and/or labeled in each illustrated view of burnerassemblies according to the present disclosure.

As shown in FIGS. 45 and/or 46, burner assembly 400 includes a housing402 within which its combustion, diffusion and distribution regions arehoused. In the illustrated embodiment, housing 402 has a generallycylindrical configuration and includes a mount 404 that is sized tocouple the burner assembly with a fuel processor. As shown, mount 404takes the form of a reduced-diameter neck 406, although it is within thescope of the disclosure that the mount may have other configurations,such as projecting flanges, struts, threads, and the like, and that thehousing may be formed without a mount. It is also within the scope ofthe disclosure that housing 402 may have any other suitable shape andthat the housing may be formed from a greater number of components thanis shown in FIGS. 45 and/or 46. Also shown are a fuel supply conduit 408for combustible fuel stream 64 (such as gaseous combustible fuel stream276) and an air supply conduit 410 for air stream 74. In the illustratedembodiment shown in solid lines, the burner assembly is adapted toreceive only gaseous combustible fuel streams. However, a vaporizingheating assembly 296, supply conduit 411 for a liquid combustible fuelstream 82, and optional partition 342 are shown in dashed lines andwould generally be present in a version of burner assembly 400 that isconfigured to receive and vaporize a liquid combustible fuel stream.

Burner assembly 400 also demonstrates another suitable configuration fortubes 314 and gas distribution manifold (or plenum) 310. Unlike thepreviously illustrated embodiments, such as illustrated in FIGS. 43 and44, in which tubes 314 extended from apertures 312 in manifold 310,burner assembly 400 demonstrates that the tubes may project though theapertures in manifold 310. As such, tubes 314 include inlets 412 thatare located within vaporization region 292.

As perhaps best seen in FIG. 45, the burner assembly includes aplurality of tubes 314 concentrically positioned within a correspondingplurality of apertures 326 in combustion distribution manifold 324.Although not required, burner assembly 400 illustrates that manifold 324may include a portion 420 proximate air input port 320 that contains noapertures and corresponding tubes, or proportionally less apertures andtubes. As shown, portion 420 corresponds to an area where thedistribution of apertures 326 (and therefore tubes 314) would be presentin a symmetrical distribution. However, portion 420 corresponds to anarea where the apertures are asymmetrically distributed, and as shown inFIG. 45, not present. A benefit of this configuration is that absence(or optional reduced number) of apertures 326 in manifold 324 proximateinput port 320 promotes the distribution of the air stream throughoutair distribution chamber 322.

FIGS. 45 and 46 also demonstrate that burner assemblies 262 according tothe present disclosure may include a chamber, or passage, 422 throughwhich ignition source 88 may be mounted and/or inserted into and removedfrom the burner assembly. When ignition source 88 is within passage 422it will tend to be shielded from direct contact with the flames that areproduced as the fuel streams are ignited. Although not required, it canbe seen in FIGS. 45 and 46 that the air streams 74′ surrounding thepassage 422 will provide a flow of air that will tend to shield theignition source from the flames produced as the fuel streams areignited.

As perhaps best seen in FIG. 46, passage 422 extends through the burnerassembly to base 340, thereby enabling the ignition source to be removedfrom a burner assembly that is mounted (such as via a mount 404) to afuel processor. A benefit of this construction is that ignition sourceswhich require periodic servicing or replacement may be used with burnerassemblies according to the disclosure without requiring the entireburner assembly to be removed from the fuel processor simply to inspect,service or remove/replace the ignition source. Instead, and as perhapsbest seen in FIG. 46, the ignition source may be inserted within thepassage, and selectively removed therefrom through base 340, such as forinspection, maintenance or replacement.

A variation of burner assembly 400 is shown in FIGS. 47 and 48. Asshown, the burner assembly includes a sleeve 430 that extends fromvaporization region 292 through combustion region 92 and into which oneor more temperature sensors 432, such as thermocouples or other suitabletemperature sensors, may be inserted. The inclusion of temperaturesensors enables the operating state of the burner assembly to bedetermined by a processor or other suitable monitor in communicationwith sensor(s) 432. For example, the sensor(s) may be used to detect ifcombustion has commenced in the combustion region. As another examples,if the burner assembly is no longer generating (or maintaining) heat,such as if the supply of combustible fuel has been interrupted, theflames have been extinguished, etc., this may be detected using thetemperature sensors. Furthermore, the measured temperatures from one ormore regions of the burner assembly may be used to control or adjust theoperating state of the burner assembly. For example, when the burnerassembly is initially preheated by vaporization heating assembly 296 (aswill be discussed subsequently), a temperature sensor 432 may be used todetermine when a selected preheat temperature has been reached. Asanother possible, but not required, application of temperature sensors432, the sensors may be used for safety reasons, namely, to sense if aregion of the burner assembly has exceeded a predetermined thresholdtemperature. Sleeve 430 may also be referred to as a sensor port or amount for one or more thermocouples or other temperature sensors.

In the illustrated embodiment, sleeve 430 defines a passage 434 that isaccessible through base 340 of the burner assembly. Similar to the abovediscussion regarding passage 422, this configuration enables temperaturesensors or other measuring equipment to be inserted into and removedfrom the burner assembly while the burner assembly is mounted on a fuelprocessor. In the illustrated embodiment, sleeve 430 extends througheach of the above-discussed regions of the burner assembly, therebyenabling the temperature of each of these regions to be selectivelymeasured through the insertion of suitable sensors 432 at theappropriate location within the sleeve. Also shown in FIG. 48 is a mount436 that retains sleeve 430 and/or sensor(s) 432 within the burnerassembly.

In FIGS. 49-51, another version of the burner assemblies of FIGS. 45-48is shown and generally indicated at 400′. As shown, the burner assemblyis adapted to receive and vaporize a liquid combustible fuel stream 82through liquid fuel supply conduit 411. Burner assembly 400′ may beconfigured to only receive liquid combustible fuel streams, in whichcase supply conduit 408 and its corresponding input port may be omitted.Similarly, although the previously discussed passage and sleeve 430 areshown in FIGS. 49-51, burner assembly 400′ may be formed without thesecomponents and/or with any of the other elements, subelements and/orvariations described and/or illustrated herein.

In FIG. 49, the burner assembly is shown including a vaporizationheating assembly 296 that includes a plurality of ports, or mounts, 460that are adapted to receive electrically powered heaters 462, such aselectric resistance heaters. As shown, heating assembly 296 includesfour ports 460, but it is within the scope of the disclosure that thenumber and configuration of the ports may vary. For example, even in thecontext of electrically powered resistance heaters, such heaters canhave disc or flat configurations, as opposed to the cylindricalcartridge heaters shown in FIG. 50. Similarly, the power requirementsand/or heat output of the heaters may affect the number andconfiguration of heaters to be used. In FIG. 50, heaters 462 are shownreceived within the ports and include electrical leads 464 that areconnected to a source of electricity, such as a battery, fuel cellstack, electrical outlet, generator, etc.

Heating assembly 296 preferably heats the vaporized fuel stream to asufficient temperature that the stream does not condense prior to beingignited in combustion region 92. As such, heating assembly 296 may beconfigured to superheat the vaporized fuel stream. For liquidcombustible fuel streams containing methanol, or optionally methanol andup to 50 vol % water, four heaters 462 that are designed to output 100watts at 10.6 volts have proven effective. It should be understood,however, that the number of heaters and/or amount of heat to be suppliedtherefrom will tend to vary depending upon the composition of the liquidcombustible fuel stream, the flow rate thereof, and/or the configurationof the vaporization region. The heaters may be configured to provide aconstant output, or alternatively may be selectively controlled toprovide a selected amount of heat from within a predetermined range ofoutputs. For example, by selectively energizing between none and all ofthe heaters, the output of the heating assembly is varied. As anotherexample, the power provided to the heaters may be controlled, such as bypulse width modulation of the DC voltage delivered thereto toselectively scale the power.

When heaters 462 are removably received within the vaporizing heatingassembly, the heating assembly may (but is not required to) include asuitable retainer 466 that is adapted to retain the heaters therein andthereby prevent unintentional removal of the heaters. An illustrativeexample of a suitable retainer 466 is shown in FIGS. 50 and 51 in theform of a pin 468 that is selectively passed through guides 470 that arepositioned so that the openings of the ports are at least partiallyobstructed by the pin after the pin is inserted through the guides. Insuch a configuration, vaporizing heating assembly 96 may include atleast one such pin 468 at each end of the ports. As a variation of thisconfiguration, the mounts may be keyed so that the heaters may only beinserted into (or removed from) one end of the ports. For example, oneend of the ports may be obstructed, or even closed, so that the heaterscannot pass completely through the ports.

FIG. 50 also demonstrates an example of a modular, or cartridge-based,ignition source 88 that may be selectively inserted into and removedfrom operative positions relative to combustion region 92 via passage422. As shown, the ignition source includes a housing 480 within whichthe particular igniting element(s) 482 is/are located. For example,housing 480 may contain a combustion catalyst, spark plug, electricallyheated ceramic element, etc. As shown, housing 480 includes a mount 484that is adapted to be releasably coupled to the burner assembly, such asto base 340.

In FIGS. 52 and 53, another example of a burner assembly 262 accordingto the present disclosure is shown and generally indicated at 500. Inthe illustrated embodiment, burner assembly 500 is adapted to receive agaseous combustible fuel stream through fuel port 302 and an air streamthrough air post 320. However, it is within the scope of the disclosurethat burner assembly 500 may additionally or alternatively receive aliquid combustible fuel stream through port 302 or an additional portwithin vaporization/staging region 292, with burner assembly 500 in suchan embodiment also being heated such that the liquid fuel is vaporizedin region 292. As perhaps best seen in FIG. 53, burner assembly 500demonstrates a bifurcated, or distributed, air distribution chamber 322.More specifically, and as perhaps best seen in FIG. 53, an air stream isdelivered into a primary distribution region 510, which in theillustrated embodiment takes the form of an annulus that surrounds tubes314 and is separated therefrom by a wall structure 512. As shown, wallstructure 512 includes a plurality of ports 514 through which the airstream may be introduced into a secondary distribution region 516, inwhich the air stream may flow around the tubes and be distributedbetween the apertures 326 in combustion distribution manifold 324.Preferably, ports 514 are spaced at intervals around wall structure 512so that air entering region 510 is circulated within the region andintroduced into secondary distribution region 516 from a plurality ofradially spaced-apart ports. The distributed design of air distributionchamber 322 is designed to promote distribution of the air streamthroughout region 516.

As discussed, burner assembly 500 may be adapted to receive and vaporizea liquid combustible fuel stream. An illustrative example of such aversion of the burner assembly is shown in FIG. 54 and generallyindicated at 500′. As shown in solid lines, the burner assembly includesa vaporizing heating assembly 296 and is adapted to receive a liquidcombustible fuel stream through an input port, such as the port that waspreviously utilized for a gaseous combustible fuel stream in FIG. 52.When the burner assembly is adapted to selectively receive either orboth of gaseous and liquid combustible fuel streams, vaporization region292 will typically include a pair of fuel input ports, with the secondsuch port indicated in dashed lines in FIG. 54. Although vaporizingheating assembly 296 has been illustrated in FIG. 54 as being mountedon, or integrated with, the rest of burner assembly 500′, such as beingwithin or forming a portion of a common shell or housing 402, it iswithin the scope of the disclosure that vaporizing heating assembly 296may be a separate structure that is merely positioned to deliversufficient heat to the vaporization region to vaporize the liquidcombustible fuel stream. For example, instead of generating heat itself,such as electrically or through combustion, the heating assembly maydeliver a heated fluid stream that vaporizes the liquid combustible fuelstream.

In operation, burner assemblies 262 according to the present disclosurethat are adapted to receive a liquid combustible fuel stream (eitheralone or in combination with a gaseous combustible fuel stream) aretypically preheated, such as by vaporizing heating assembly 296. Areason for preheating the burner assembly is so that the liquidcombustible fuel stream does not fill or overflow the vaporizationregion while the region is heated. For most suitable liquid fuels, suchas alcohols and shorter chain hydrocarbons, preheating the vaporizationregion to at least 150° C. and typically less than 500° C. has proveneffective. Preheating the vaporization region to approximately 200-250°C. has proven particularly effective for methanol and methanol/waterliquid combustible fuel streams. Although not required, it may bedesirable to preheat the vaporization region to a temperature that willproduce thin film boiling of the liquid combustible fuel stream that isdelivered thereto.

As discussed, burner assemblies 262 according to the present disclosuremay be used to heat the hydrogen-producing regions of a variety of fuelprocessors. For purposes of illustration, the following discussion willdescribe a liquid/gaseous burner assembly according to the presentdisclosure being used with a fuel processor in the form of a steamreformer that is adapted to receive a feed stream 16 containing acarbon-containing feedstock and water. However, it is within the scopeof the disclosure that fuel processor 12 may take other forms, asdiscussed above. An example of a suitable steam reformer isschematically illustrated in FIG. 55 and indicated generally at 530.Reformer 530 includes a hydrogen-producing region 19 in the form of areforming region that includes a steam reforming catalyst 23. In thereforming region, a resultant stream 20, which may in this context alsobe referred to as a reformate stream, is produced from the water andcarbon-containing feedstock forming feed stream 16.

As discussed previously, feed stream 16 may be a single streamcontaining both water and a water-soluble carbon-containing feedstock,or it may be two or more streams that collectively contain the water andcarbon-containing feedstock(s) that are consumed in the reformingregion. As shown in dashed lines in FIG. 55, it is within the scope ofthe disclosure that at least the carbon-containing feedstock componentof feed stream 16 may also form a combustible fuel stream 64 that isdelivered to burner assembly 262. It is also within the scope of thedisclosure that the complete feed stream (i.e. water andcarbon-containing feedstock) may be used as the combustible fuel streamfor burner assembly 262. For example, a reforming feed stream maycontain approximately 50-75 vol % methanol and approximately 25-50 vol %water. An example of a particularly well-suited feed stream contains 69vol % methanol and 31 vol % water. This stream may effectively be usedas the feed stream for reformer 530 and the combustible fuel stream fora burner assembly according to the present disclosure. A benefit of thiscommon feed/fuel is that the overall size of the fuel processing systemmay be reduced by not having to store and deliver a fuel stream 64having a different composition than feed stream 16 (or its components).

When a burner assembly 262 is used to heat steam reformer 530 from anoff, or cold, state, the burner assembly is initially preheated usingvaporizing heating assembly 296. As an illustrative example, reformersthat receive a feed stream 16 containing methanol will typically bepreheated to at least 300° C., and more preferably, 325-350° C. Afterthis temperature is reached, a liquid combustible fuel stream 82 isdelivered to the vaporization region and vaporized, and an air stream 74is delivered to distribution region 284. The vaporized fuel streams andair streams are distributed, diffused together and ignited, as discussedherein, with the resulting hot combustion stream 66 being used to heatat least the reforming region of steam reformer 530.

When the reforming region has been heated to a predetermined reformingtemperature, which as discussed will tend to vary depending upon thecomposition of feed stream 16, feed stream 16 is delivered to thereforming region to produce reformate stream 20. Although feed stream 16(or at least the carbon-containing feedstock component thereof) maycontinue to be used as the combustible fuel stream for the burnerassembly, at least part, or even all, of the fuel stream may be formedby byproduct stream 28. In such an embodiment, the burner assembly willinitially be used with a liquid combustible fuel stream during startupof the reformer, and then will be used with a gaseous burner assemblyafter the reforming region is preheated and producing a reformatestream.

This illustrative utilization of a burner assembly 262 is depicted inflow chart 560 in FIG. 56. As shown, at 562, the burner assembly ispreheated. At 564, the burner assembly preheats the reforming regionusing a liquid combustible fuel stream. As discussed, this fuel streammay contain the same composition as the feed stream for the reformer. At566, the preheated reforming region receives a feed stream containing acarbon-containing feedstock and water. The feed stream is reformed toproduce a reformate stream containing hydrogen gas and other gases. At568, the reformate stream is separated into a hydrogen-rich stream and abyproduct stream, and at 570, the byproduct stream is delivered to theburner assembly for use as a gaseous combustible fuel stream. If thebyproduct stream contains sufficient heating value to maintain thereforming region at a suitable reforming temperature, then the flow ofliquid combustible fuel stream may be stopped. When byproduct stream 28does not contain sufficient heating value, it may be supplemented, suchas with another gaseous combustible fuel stream (including a portion ofreformate stream 20, hydrogen-rich stream 26 or product hydrogen stream14) and/or the liquid combustible fuel stream may continue to bedelivered to the burner assembly, typically at a reduced flow comparedto its startup flow rate. It should be understood, however, that theabove implementation is but one of many uses for burner assembliesaccording to the present disclosure.

INDUSTRIAL APPLICABILITY

Burner assemblies, steam reformers, fuel processing systems and fuelcell systems according to the present disclosure are applicable to thefuel processing, fuel cell and other industries in which hydrogen gas isproduced, and in the case of fuel cell systems, consumed by a fuel cellstack to produce an electric current.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. Similarly, where theclaims recite “a” or “a first” element or the equivalent thereof suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and subcombinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and subcombinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A method for operating a hydrogen-producing fuel processing system,the method comprising: heating a hydrogen-producing region of a fuelprocessing system to hydrogen-producing temperature of at least 350° C.,wherein the hydrogen-producing region contains a catalyst adapted tocatalyze the formation of a mixed gas stream comprising hydrogen gas asa majority component from water and a carbon-containing feedstock via anendothermic reaction at the hydrogen-producing temperature; providing afeed stream comprising water and a carbon-containing feedstock to thehydrogen-producing region; producing the mixed gas stream in thehydrogen-producing region via the endothermic reaction catalyzed by thecatalyst, wherein the mixed gas stream further comprises other gases;delivering a fuel stream and an air stream to a heating assembly;combusting the fuel stream to produce a hot combustion stream; heatingat least the reforming region with the hot combustion stream to maintainthe reforming region at a temperature of at least the hydrogen-producingtemperature; and controlling the rate at which the air stream isdelivered to the heating assembly to selectively increase or decreasethe temperature of the hot combustion stream produced by the heatingassembly.
 2. The method of claim 1, wherein the controlling includescontrolling the rate at which the air stream is delivered to the heatingassembly independent of the flow rate of the feed stream to thehydrogen-producing region.
 3. The method of claim 1, wherein thecontrolling includes controlling the rate at which the air stream isdelivered to the heating assembly without actively controlling the rateat which the feed stream is delivered to the hydrogen-producing region.4. The method of claim 1, wherein the controlling includes controllingthe rate at which the air stream is delivered to the heating assemblyindependent of the flow rate of the fuel to the heating assembly.
 5. Themethod of claim 1, wherein the controlling includes controlling the rateat which the air stream is delivered to the heating assembly withoutactively controlling the rate at which the fuel is delivered to theheating assembly.
 6. The method of claim 1, wherein the deliveringincludes delivering the air stream at a rate sufficient to provide atleast 200% of a stoichiometrically required amount of oxygen gas tocombust the fuel to produce the hot combustion stream.
 7. The method ofclaim 1, wherein the method includes increasing the rate at which theair stream is delivered to the heating assembly without decreasing therate at which the fuel is delivered to the heating assembly to produce acooler hot combustion stream.
 8. The method of claim 1, wherein themethod further comprises separating the mixed gas stream into a producthydrogen stream containing at least substantially pure hydrogen gas andat least one byproduct stream containing at least a substantial portionof the other gases, and further wherein the fuel includes the byproductstream.
 9. The method of claim 8, wherein the separating includesutilizing at least one hydrogen-selective membrane to separate the mixedgas stream into the product hydrogen stream and the byproduct stream.10. The method of claim 8, wherein the separating includes utilizing apressure swing adsorption assembly to separate the mixed gas stream intothe product hydrogen stream and the byproduct stream.
 11. Ahydrogen-producing fuel processing system, comprising: ahydrogen-producing region containing a reforming catalyst and adapted toreceive a feed stream containing at least a carbon-containing feedstockand to produce a mixed gas stream containing hydrogen gas and othergases therefrom; a burner assembly adapted to produce a hot combustionstream for heating at least the hydrogen-producing region of the fuelprocessing system, wherein the burner assembly is adapted to receive acombustible fuel stream and an air stream and to combust the fuel andair streams to produce the hot combustion stream, wherein thecombustible fuel stream is comprised of at least one of the feed streamand at least a portion of the mixed gas stream; and means forselectively increasing and decreasing the temperature of the hotcombustion stream produced by the burner assembly by controlling therate at which the air stream is delivered to the burner assemblyindependent of the flow rate of the feed stream to thehydrogen-producing region.
 12. The fuel processing system of claim 11,wherein the carbon-containing feedstock is miscible with water, andfurther wherein the fuel stream and the feed stream contain thecarbon-containing feedstock and at least 25% water.
 13. The fuelprocessing system of claim 12, wherein the fuel processing systemfurther includes a valve assembly that is adapted to receive a streamcontaining water and a liquid carbon-containing feedstock and toapportion the stream into the feed stream for the hydrogen-producingregion and the combustible fuel stream for the burner assembly.
 14. Thefuel processing system of claim 11, wherein the hydrogen-producingregion includes at least one reforming catalyst bed containing a steamreforming catalyst, and further wherein the feed stream comprises waterand the carbon-containing feedstock.
 15. The fuel processing system ofclaim 11, wherein the fuel processing system further includes at leastone separation region adapted to receive at least a portion of the mixedgas stream and to produce a hydrogen-rich stream containing at leastsubstantially pure hydrogen gas and at least one byproduct streamcontaining at least a substantial portion of the other gases.
 16. Thefuel processing system of claim 15, wherein the at least one separationregion includes a membrane module that contains a compartment into whichthe mixed gas stream is delivered under pressure, and further whereinthe compartment contains at least one hydrogen-selective membrane, thehydrogen-rich stream is formed from a portion of the mixed gas streamthat passes through the at least one hydrogen-selective membrane, andthe byproduct stream is formed from a portion of the mixed gas streamthat does not pass through the at least one membrane.
 17. The fuelprocessing system of claim 15, wherein the at least one separationregion includes a pressure swing adsorption assembly.
 18. The fuelprocessing system of claim 11, wherein the fuel processing systemincludes a plurality of reforming catalyst beds that collectively definea central combustion region into which the hot combustion stream fromthe burner assembly is received from the burner assembly, and furtherwherein the fuel processing system includes a distribution manifold thatis adapted to receive the feed stream and deliver the feed stream to theplurality of reforming catalyst beds, wherein the distribution manifoldhas a central passage through which the hot combustion stream from theburner assembly flows to the combustion region.
 19. The fuel processingsystem of claim 11, in combination with a fuel cell stack adapted toreceive at least a portion of the mixed gas stream.
 20. A fuelprocessing system, comprising: a hydrogen-producing region containing areforming catalyst and adapted to receive a feed stream containing atleast a carbon-containing feedstock and to produce a mixed gas streamcontaining hydrogen gas and other gases therefrom; a burner assemblyadapted to produce a hot combustion stream for heating at least thehydrogen-producing region of a fuel processor, wherein the burnerassembly is adapted to receive a combustible fuel stream and an airstream and to combust the fuel and air streams to produce the hotcombustion stream, wherein the combustible fuel stream is comprised ofat least one of the feed stream and at least a portion of the mixed gasstream; and means for selectively increasing and decreasing the amountof heat produced by the burner assembly by controlling the rate at whichthe air stream is delivered to the burner assembly without activelycontrolling the rate at which the feed stream is delivered to thehydrogen-producing region.